John Deere TRAILFIRE, LX, SPORTFIRE, LIQUIFIRE Snowmobile User manual

.
.
How .:To Fine Tune
.
Your 1982
AI FI~;:'s~8~f~~EE®~
Snowmobiles
J&-
JOHN DEERE
ana
~I-'UH
I t-IHI:.\!Y
Snowmobiles
Introd uction
This manual is written for John Deere dealers and
customers who are experienced snowmobilers.
NOTE: This manual is not intended to provide detailed
racing information; it is intended to provide the
information necessary to fine tune a snowmobile for various altitudes and riding conditions.
The information is presented in a cause and
effect relationship to help you understand the
effects of tuning on the performance of your
snowmobile. The procedures are not recommendations unless specifically stated as such.
This manual contains instructions for fine tuning the
carburetor, power train , and suspension system. Adjust the carburetor first, then the power train, and finally
the suspension system .
Tuning is often a process of trial and error at the
dealerIcustomer level due to a lack of sophisticated
equipment. Improved performance in one area may be
accompanied by degraded performance in another.
The object of fine tuning is to obtain the best overall
performance throughout the operating range.
NOTE: The John Deere snowmobile is carefully tuned
at the factory to provide peak performance for
average operating conditions at altitudes of
sea level to 4000 feet (1219 my. Fine tuning
can improve performance to suit specific
operating conditions and can also help compensate for the machine 's power loss at higher
altitudes.
Before performing any procedures in this manual, be
sure you have read and understand the information in
your Operator 's Manual. This manual does not contain
assembly and disassembly instructions. If you need
this information , get the appropriate Technical Manual
through your John Deere dealer.
NOTE: Some of the procedures require special tools.
These tools are described in the Technical
Manual.
IMPORTANT: All obligations of John Deere warranty shall be terminated if products
.1 I". "UU""."..
This manual is written for John Deere dealers and
customers who are experienced snowmobilers.
NOTE: This manual is not intended to provide detailed
racina information: it is intended to orovide the
1
Contents
,
CARBURETION
;.......
Principles of Operation
General Tuning Procedure
Starting System
Float System . . . . . . . . . . . . . . . . . . . , . . .
Pilot/Air System. . . . . . . . . . . . . . . . . . . . .
Throttle Valve
Jet Needle. . . . . . . . . . . . . . . . . . . . . . . . .
Needle Jet
Main Jet System
Power Jet System . . . . . . . . . . . . . . . . . . .
Compensation for Altitude and Temperature
Page
2-25
... 2
6
7
... 8
... 9
11
12
14
15
. . .17
18
POWER TRAIN
26
Drive Sprocket Ratio
27
102C Drive Sheave
28
TR800 Drive Sheave
35
Driven Sheave
.' .37
Drive Sheave and Driven Sheave ~Iignment .. .40
UQUIFIRE Chain Tensioner Adjustment ..... .41
Drive Belt Dimensions . . . . . . . . . . . . . . . . . . .42
High Altitude Application
.42
SUSPENSION
Torsion Spring Adjustment
Ski Alignment.
Ski Steering Control
Track Adjustments
Track Studs
45
45
.46
.47
47
.48
,
Page
CARBURETION
2-25
Principles of Operation
;
2
General Tuning Procedure . . . . . . . . . . . . . . . . 6
Starting System
7
Float System . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Pilot/Air System. . . . . . . . . . . . . . . . . . . . . . . . 9
Carburetion
PRINCIPLES OF OPERATION
CARBURETORS
Snowmobile
TRAILFIRE
TRAILFIRE LX
SPORTFIRE
UOUIFIRE
PTO Side
Mag Side
John Deere
Part No.
Mikuni
Part No.
AM55053
AM55054
AM55055
VM34/192
VM34/232
VM34/231
AM55436
AM55435
VM36/122
VM36/121
The TRAILFIRE snowmobiles use a standard Mikuni
Slide Valve carburetor. The UOUIFIRE and SPORTFIRE snowmobiles use a Mikuni Power Jet carburetor.
See pages 22 and 23 to familiarize yourself with the
components of each carburetor.
The Mikuni carburetors use several fuel metering systems.
Standard Slide Valve
-Starting System
- Float System
- Pilot/Air System
- Needle Jet and Jet
Needle System
- Throttle Valve
- Main Jet System
Power Jet Slide Valve
-Starting System
- Float System
-Pilot/Air System
-Needle Jet and Jet
Needle System
- Throttle Valve
-Main Jet System
-Power Jet System
By carefully matching these fuel metering systems, the
carburetor can be tuned for maximum performance
and efficiency to suit operating conditions.
These systems overlap to provide smooth transition as
the throttle moves through its full range of positions. A
change in one system can affect the performance of
other systems. Any change to the carburetor must be
evaluated to determine its effect on other fuel metering
systems.
The different fuel metering systems provide fuel at
various throttle openings as shown in the diagrams on
oaaes 3 and 4.
PRINCIPLES OF OPERATION
CARBURETORS
Carburetion
3
THROTTLE VALVE
OPENING
WI DE
........
OPEN----+-+--....,.......,--.r___lri--f--
..
3/4 ----+-tI_-fII!!!I!~+--~~
__I_+---__.~
__
1/2 - - - -....""""~-+--~-I---...._...__.......-
1/81~/4~===~~~~~~~~ff==flt-'r
CLOSED
PILOT AIR SCREW
THROTTLE VALVE-JET NEEDLE------~
NEEDLE JET ---------MAIN JET------------
M20857
M20857
Standard Slide Valve Carburetor
100
95
\
90
\
85
JI/I"
\
80
\
75
,-
\
70
3:
0
.....J
u..
.....J
w
60
:::::>
55
.....J
50
c:::e
0
45
u..
40
I0
~
,
~S'\ ."
~"\
~~
"""
" '-,- ..--'~
l\..
I'
35
/
/" ""<,
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<OJ'
I'
30
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~
~
25
,~
20
15
,
"' <,
"
....
,J
<,
I
10
5
til"
~ s/-
-,
65
u,
I-
\
St- ~"
til"
<,
•
I
0
IDLE
1/8
1/2
..
3/ 4
1/8
1/4
CLOSE D
3/8
114
,,
1/2
WOT
3/4
THROTTLE OPEN ING
\
edit
\.
1IDIrn
t""'Il
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\m 1
J
s:
(0 0
J=
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4
Carburetion
THROTTLE VALVE
OPENING
WI DE OPEN
-==1Jj~!tC::S:~~=====::!=tI~=W:=
3/4
1/2 1/4
1/8 CLOSED
PI LOT AI R SCREW
THROTTLE VALVE-----JET NEEDLE
NEEDLE JET---....J
MAIN JET
POWER JET _ _
---....J
M25733
M25733
Power Jet Carburetor
PILOT SYSTEM
r~AIN SYSTEtvl
POWER SYSTE~1
100%
90
'
......
" ..
,
80
70
FLOH
60
50
" "''"
10
0
'/'
/ ' '-.
40
30
20
»:
~
~
/'
/'
/'
o
,
~
.....
..
..
-'...
..
,..
.... ~
<,
.,
.
.
.
,.
. ........ r-- _ _ _ _
.
..
...
""IIli
"'-.
1/4
l/Z
3/4
WOT
THROTTLE SETTING
M29253
Power Jet Carburetor
WI DE OPEN
--+-+ -F~~-:::::-::::~~~-----
----._
3/4 --+-\~el&.:J?---=:~~ii!-----..~__~
1/2 1/4 -~~~~----J'---I-l~-\----,r--II~~f---it---+-
1/8 CLOSED
~\\1~~~~~§SIIa..-.
Carburetion
1. The fuel level in the bowl of the float system is the
base line.
2. The pilot/air system functions from the time the
throttle is in the closed position until it is about 1/4
open.
3. The throttle valve functions from low throttle openings to near wide open throttle.
4. The jet needle and needle jet work together to
control the midrange mixture (from approximately
1/4 to near wide open throttle).
5. The main jet system on the standard carburetor
determines the mixture at wide open throttle. This
system supplies fuel to all but the pilot/air system
through the main jet.
6. The main jet system on the power jet carburetor
determines the mixture supplied to the engine from
1/4 to wide open throttle.
7. The power jet system provides the additional fuel
required from approximately 3/4 to wide open
throttle.
."
~.
I ne mrome valve runcnons from lOW tnrorne openings to near wide open throttle.
4. The jet needle and needle jet work together to
control the midrange mixture (from approximately
1/4 to near wide open throttle).
5. The main jet system on the standard carburetor
determines the mixture at wide open throttle. This
system supplies fuel to all but the pilot/air system
5
6
Carburetion
GENERAL TUNING PROCEDURE
The best way to evaluate the tuning of a carbureto r is
by operating the snowmobile.
IMPORTANT: Operating an engine with too lean a
fuel mixture may cause engine
damage.
Bogging , popping, or spitback during acceleration indicates a lean fuel/air mixture. Because the internal
cooling of the engine depends on the fuel to some
extent, a fuel/air mixture which is too lean can cause
engine overheating.
Excessive smoking or rough engine operation indicates a rich fuel/air mixture .
If you cannot determine if the fuel/air mixture is too rich
or too lean, assume a too lean condition and tune
accordingly.
When changing parts in a carburetor , keep dirt out of
the system. Dirt can clog jets and destroy the performance of a well-tuned carburetor.
Tune the carburetor by performing the following steps
in the sequence given. Because a change in one
system can affect the performance of other systems,
checks of related fuel metering systems must be made
frequently throughout the tuning procedure . For high
altitude applications, refer to the charts on pages 18
and 19.
IMPORTANT: All tuning on snowmobiles must be
performed with the air intake silencer in place. If not, false readings will
result which may cause serious engine damage.
oy operating me snowmobi le.
IMPORTANT: Operating an engine with too lean a
fuel mixture may cause engine
damage.
Bogging, popping, or spitback during acceleration indicates a lean fuel/air mixture . Because the internal
cooling of the engine depends on the fuel to some
extent, a fuel/air mixture which is too lean can cause
Carburetion
Tuning the Carburetor
1. Check the position of starter plunger (see below).
2. Make sure floats are properly adjusted (page 9).
3. Operate snowmobile at wide open throttle and
check operation of main jet system (page 15) and
power jet system (page 17). If main jet or power jet
is changed by several sizes, recheck jet needle and
needle jet.
4. Operate engine between idle and 1/4 throttle and
check engine operation . Flip choke lever momentarily to provide excess fuel. If engine operation
improves, more fuel is needed. If engine operation
becomes worse, less fuel is needed. When carburetor is properly tuned there will be very little effect.
If adjustment is necessary, perform Step 5 (also see
page 10).
5. Check and adjust air screw setting (page 10). If
required, change pilot jet (page 10) and readjust air
screw.
6. Use air screw adjustment to check for proper throttle valve selection (page 11).
IMPORTANT: Except for extreme running conditions, the needle jet should not be
changed.
7. Operate snowmobile at mid-throttle settings and
check operation of jet needle (page 12) and needle
jet (page 14).
B. Operate snowmobile through all throttle settings.
Check for smooth operation.
STARTING SYSTEM
Principles of Operation
When raised, the starter plunger allows fuel to be
metered through starter jet and mixed with air. This
fuel/air mixture flows into plunger area, mixes with
more air from air intake port used for starting, and is
then drawn into engine. The throttle must be closed for
this starting system to operate.
Adjusting Starter Plunger
1. Inspect starter plunger to make sure it is seated
when choke lever (on dash) is in the off (or down)
position. Choke cable should have a 0.060 to
O.OBO-inch (1 .524 to 2.032 mm) end play.
2. Adjust starter plunger so it rises approximately 1/2
of bore. diameter when choke lever..is lifted Jo the
power jet system (page 17). If main jet or power jet
is changed by several sizes, recheck jet needle and
needle jet.
4. Operate engine between idle and 1/4 throttle and
check engine operation . Flip choke lever momentarily to provide excess fuel. If engine operation
improves, more fuel is needed. If engine operation
becomes worse, less fuel is needed. When carbuI
&.
_
.&.1
• __
~II
L-.
_ .
~
I ~.&..I.'_
-.U _ _ .a.
7
8
Carburetion
FLOAT SYSTEM
Principles of Operation
The float system maintains the correct fuel level in the
float bowl under all engine operating conditions .
The float system uses two floats to counteract side-toside movement and high and low operating angles of
the snowmobile . When the fuel level drops in the float
bowl, the floats and float arm with actuating tab also
drop, opening the needle valve. The fuel pump forces
fuel from the fuel tank past the needle valve into the
float bowl. As the fuel in the float bowl approaches the
correct level, the floats rise, causing the needle valve
to seat, shlJtting off the fuel flow.
Under operating conditions, the needle valve and floats
position themselves so that inward flow of fuel to the
carburetor float bowl is equal to the outward flow of fuel
to the engine.
M25734 "
float bowl under all engine operating conditions.
The float system uses two floats to counteract side-toside movement and high and low operating angles of
the snowmobile. When the fuel level drops in the float
bowl, the floats and float arm with actuating tab also
drop, opening the needle valve. The fuel pump forces
fuel from the fuel tank past the needle valve into the
float bowl. As the fuel in the float bowl approaches the
corraot lAVAl thp.
fln~tc: ric:o
1"'~IIc:inn tho noorUo \I~I\lO
Carburetion
~~~aL
I
Checking and Adjusting Float System
1. Invert the carburetor and check the alignment between the float arm and the base of the carburetor.
The float arm should be parallel to the base.
.-..r"'" ......
2. Bend the actuating tab as required to make the float
arm parallel to the base . Be careful not to bend the
float arm.
NOTE: Incorrect float adjustment can prevent proper
tuning of a carburetor. Always make sure the
float is properly adjusted before attempting
adjustment of the other fuel metering systems.
::f::~ HI
PARA'LLEL
I~
HIGH FLOAT SETTING
I
o WILL RESULT IN HARD
I
-t-
-
STARTING -=..!!CH RUNNIJG
LOW FLOAT SETTING
o WILL RESULT IN HARD
STARTING - LEAN RUNNING
I
I
~
M25?35
I~
lJ\-~~r-~~
PILOT I AIR SYSTE M
Principles of Operation
The pilot/air system controls the fuel mixture between
idle and approximately the 1/4 throttle position. As the
throttle is opened wider for low speed operation, the
pilot outlet cannot supply adequate fuel, and the fuel
then enters the carburetor bore from the bypass as well
as the pilot outlet. The pilot/air system is tuned by first
adjusting the air screw: then, if necessary, by replacing
the pilot jet (page 10).
M27423
(111"
IJ(1r(1I1~1
lV
1I1~
U(1:)~. D~ l;dl~IUI
IIVL LV
U~IIU
1I1~
float arm.
NOTE: Incorrect float adjustment can prevent proper
tuning of a carburetor. Always make sure the
float is properly adjusted before attempting
adjustment of the other fuel metering systems.
II
I
-t-
..
, -;IG;F~ATI Sm¥NG ~
o WILL RESULT IN HARD
STARTING -=..!!CH RUNNIJG
LOW FLOAT SETTING
o WILL RESULT IN HARD
STARTING - LEAN RUNNING
I
I~
9
10
Carburetion
PILOT/AIR SYSTEM-Continued
Adjusting Air Screw
NOTE: This procedure may be performed for single
and dual carburetors. On dual carburetors,
both air screws must be adjusted exactly the
same. Never adjust the screws more than 1/4
turn at a time.
1. Turn idle stop screw in until screw contacts throttle
valve. Then turn idle stop screw in 2 additional
turns .
2. Start and warm up engine . Adjust idle stop screw to
500 rpm above normal idle speed. See pages 18
and 19.
M20863
NOTE: Set idle speed at 3500 rpm on UOUIFIRES
with speed limiter systems.
3. Turn air screw in or out using 1/4-turn increments
until engine rpm peaks or reaches its maximum
rpm.
4. Readjust idle stop screw to return engine to normal
idle speed. See pages 18 and 19.
5. Repeat Steps 3 and 4 until engine operates at
normal idle speed and air screw is peaked.
6. When air screw is adjusted stop engine. Note the
setting of air screw and turn it all the way in. If it
takes less than 1 turn, the pilot jet is too small and a
larger one must be installed. If it takes more than
2-1/2 turns to seat air screw , the pilot jet is too large
and must be replaced by a smaller one.
Replacing Pilot Jet
~~ IPILOT
JET
"
Pilot jets are numbered from No. 15 (the smallest) to
No. 80 (the largest). The number corresponds to fuel
flow and not necessarily to drill size or through-hole
diameter.
After changing the pilot jet, check and adjust air screw
as described above.
NOTE: Since the pilot/air system provides some fuel
up to wide open throttle, changes in this system will affect the throttle valve, jet needle/
needle jet, and main jet metering systems .
and dual carburetors. On dual carburetors,
both air screws must be adjusted exactly the
same. Never adjust the screws more than 1/4
turn at a time.
1. Turn idle stop screw in until screw contacts throttle
valve . Then turn idle stop screw in 2 additional
turns .
2. Start and warm up engine. Adjust idle stop screw to
Carburetion
THROTTLE VALVE
Principles of Operation
The throttle valve is cut away on the air inlet side to
help control the fuel/air mixture at low and intermediate
throttle settings. The size of the cutaway also affects
acceleration.
~
Throttle valves are numbered from 0.5 to 4.5 in 0.5
increments based on the size of the cutaway. The most
commonly used configurations are 1.5 to 3.5. The
higher the number, the greater the cutaway and the
larger the air flow.
-1-- J_
Tlie throttle valve functions in about the same range as
the pilot/air system. After the air screw is adjusted, it
can be used to check the throttle valve selection.
-2.0
3.0
-f-f-
Checking and Selecting Throttle Valve
1. Operate engine at low throttle settings, accelerating
from idle to 1/4 throttle.
THROTTLE
VALVE
M25737
2. If engine bogs during acceleration, there is probably
insufficient fuel. Turn in air screw about 1/4 turn at a
time. If engine acceleration is improved, after adjusting air screw, the throttle valve cutaway needs
to be decreased.
3. If engine runs rough or smokes excessively during
acceleration, there is probably too much fuel. Turn
out air screw 1/4 turn at a time. If engine operation
is improved, the throttle valve cutaway needs to be
increased.
NOTE: Illustration at right indicates fuel flow by throttle
valve size and the amount throttle valve is
opened.
4. Increase or decrease throttle valve cutaway size in
0.5 steps.
5. Return air screw to its original setting and operate
engine at low throttle settings. Accelerate engine
from idle to 1/4 throttle; engine should accelerate
smoothly.
6. As a final check, change the position of the air
screw. If this does not significantly affect engine
performance (as in Steps 2 and 3), the throttle valve
is correct.
5
M27230
15
25
50
15
Throttle valve opening (%)
acceleration.
THROTTLE
~ VALVE
Throttle valves are numbered from 0.5 to 4.5 in 0.5
increments based on the size of the cutaway. The most
commonly used configurations are 1.5 to 3.5. The
higher the number, the greater the cutaway and the
larger the air flow.
Tlie throttle valve functions in about the same range as
the oilot/air svstem. After the air screw is adiusted. it
100
/'
./
/'
-1-- J_
?n
3.0
11
12
Carburetion
JET NEEDLE
Principles of Operation
~2
"'.
The jet needle works with the needle jet to increase the
amount of fuel as the throttle valve is raised.
~3
Although the jet needle and needle jet function in the
1/4 to 3/4 throttle range, they also affect the amount of
fuel present at wide open throttle. When tuning the jet
needle, also check main jet system operation (page
15).
.
15
M27231
75
Throttle valve opening (%)
50
100
The jet needle raises and lowers with the throttle valve
which changes jet needle position in the needle jet.
Because the jet needle is tapered from top to bottom,
an increasing amount of fuel is delivered through the
needle jet whenever the throttle valve is raised. Increased or decreased air flow, by the throttle valve
position, regulates the amount of fuel through the
needle jet and around the jet needle.
The jet needle works on a combination of length, taper,
and E-ring position. Each jet needle has a number and
letter series stamped on the body.
__ ._ , __ ••
._ ..
~
•• ,,'" ... ~ . . . . .'" IlvvUlv JvL LV
1I1"'1t::c1~~ UJ~
amount of fuel as the throttle valve is raised.
Although the jet needle and needle jet function in the
1/4 to 3/4 throttle range, they also affect the amount of
fuel present at wide open throttle. When tuning the jet
needle, also check main jet system operation (page
15).
Carburetion
Example: 60H7
6
...."",•.-.._ 1
....--- -2
4--1iiii:i::::r--
- Basic length of needle.
3
OH - A single letter would indicate a single taper of
the needle, double letter a double taper.
o - Amount of taper
o
at top of needle.
H - Amount of taper at bottom of needle.
7
T
5
~
•
- Material, type of coating and start of second
taper on needle.
I
NOTE: Letter designation of the jet needle indicates
the angle of taper. Each letter (starting with A)
is 0.25° greater than preceding letter. Example: 0 = 1°, E = 1-1/4°, F = 1-1/2°, G = 1-3/4°,
and H = 2°. This applies to both single and
double taper needles.
At the top of the jet needle are five grooves numbered
1 through 5 from top to bottom-the number 3 or
middle groove being the starting point for the E-ring.
The E-ring position on any jet needle determines the
rich or lean part throttle or mid-range carburetor
operation.
H
I
M27233
Moving E-ring to position 1 or 2 lowers jet needle into
needle jet and leans out the fuel/air mixture. Similarly,
moving E-ring to position 4 or 5 raises jet needle in
needle jet and enriches the fuel/air mixture.
,
Positioning E-Ring
LEAN
1. Check for a rich or lean setting by examining the
muffler ball joint (page 15). A very light brown or
white color indicates a lean mixture. A very dark
brown or black color indicates a rich mixture. The
proper color is tan.
2. Move E-ring one groove at a time to correct the
fuel/air mixture.
3. If proper operation is obtained at all but the 3/4
throttle setting after the main jet has been tuned,
operation may be improved by changing the jet
needle taper. Do not, however, change the jet needle until main jet and E-ring position have been
thoroughly checked.
4. If the E-ring is in the number 5 position and operation is still lean, a needle jet with a larger orifice may
be installed. This may be done only after thoroughly
checking the main jet, jet needle, and E-ring positions.
RICH
NUMBER
STAMPED
HERE
E-RING
WASHER
M25739
NOTE: Make sure washer is installed under E-ring.
H - Amount of taper at bottom of needle.
7
- Material, type of coating and start of second
taper on needle.
NOTE: Letter designation of the jet needle indicates
the angle of taper. Each letter (starting with A)
is 0.25° greater than preceding letter. Example: 0 = 1°, E = 1-1/4°, F = 1-1/2°, G = 1-3/4°,
__ -J l.J
"'0
T ....:
1: __
4-_
'-_"'l-. _:__ 1
-1
•
.-L
I
H
I
13
Carburetion
14
NEEDLE JET
Principles of Operation
~
The needle jet works in combination with the jet needle
to meter the fuel flow in the midrange.
Changes to the needle jet should be made only if the
results of changing the jet needle position are unsatisfactory. In stock applications, except for specific calibration changes necessary at high altitudes, the needle jet should not be changed. Selection of the proper
needle jet requires much care and experience. Decreasing the needle jet size can prevent the main jet
from metering the proper amount of fuel at wide open
throttle.
I
M20868
t
c..!'
3Z
01-0--4
--J V")
LL.c:::e
W
--J 0::::
wu
::::> Z
LL. 1-0--4
I
I--------r---------~~
MAJOR
J
CHANGE
MINOR CHANGE-
-T--
6
M20869
t.
- INCREAS ING-----...
NEEDLE JET SIZE
(X)
ci..
o
"
Needle jets are stamped with an alphanumeric code.
The letter indicates a major change in fuel flow. P-2, for
example, indicates low flow; P-4, greater flow, and so
on. The number indicates minor adjustments in fuel
flow. The diagram at left shows the relationship between the alphanumeric needle jet size number and
fuel flow.
NOTE: Needle jets carry the numbers 166, 159 or 169
in addition to the P-2 or P-4 and are not
interchangeable. Be sure correct needles are
used as specified per snowmobile.
The needle jet works in combination with the jet needle
to meter the fuel flow in the midrange.
Changes to the needle jet should be made only if the
results of changing the jet needle position are unsatisfactory. In stock applications, except for specific calibration changes necessary at high altitudes, the needle jet should not be changed. Selection of the proper
needle jet requires much care and experience. De-
Carburetion
MAIN JET SYSTEM
Principles of Operation
The main jet system starts to function when the throttle
is approximately 1/4 open. The midrange fuel is supplied by the main jet and regulated by the needle jet/jet
needle combination. The main jet meters the fuel when
the throttle is in the wide open position.
The main jets are available in sizes from number 50 to
number 500. The size number corresponds to flow and
not necessarily to hole size.
When experiencing erratic operation or overheating,
check the main jet for dirt which can plug the orifice .
Tuning Main Jet System
Before operating the snowmobile, make sure all parts,
including clutch and drive belt, are in good operating
condition.
1. Operate snowmobile at wide open throttle for several minutes on a flat, well-packed surface. Change
main jet if snowmobile fails to achieve maximum
rpm or labors at high rpm.
2. Continue to operate at wide open throttle and shut
off ignition before releasing throttle. Remove muffler
and inspect inside of ball joint area for correct color
(tan) which indicates correct mixture.
M208?O
Standard Carburetor
------------+20-22(%)
+8-10(%)
-8-10(%)
-20-22(%)
NOTE: Do not change jet sizes by more than one
increment (step) at a time.
3. If ball joint is dark brown or black, the fuel/air
mixture is too rich. Decrease jet size.
4. If the ball joint is very light in color, the fuel/air
mixture is too lean. Increase jet size.
47.5
50
75
100
Throttle valve opening (%)
M27235
,
--
--.- y
-
. _
--
- -
--..-
plied by the main jet and regulated by the needle jet/jet
needle combination. The main jet meters the fuel when
the throttle is in the wide open position.
The main jets are available in sizes from number 50 to
number 500. The size number corresponds to flow and
not necessarily to hole size.
When experiencing erratic operation or overheating,
check the main iet for dirt which can olua the orifice.
NEEDLE JET
II
I
JET NEEDLE
~ METERED I
HERE,-,AI R
15
16
Carburetion
MAIN JET SYSTEM-Continued
5. If you cannot determine the color, proceed as if
fuel/air mixture is too lean and increase jet size. If
operation improves, continue to increase jet size to
obtain peak performance. If operation becomes
worse, decrease jet size to obtain peak performance.
6. After proper main jet is selected, recheck jet needle
and needle jet.
MAIN JET
M25?40
M25 740
Power Jet Carburetor
iuerz arr mixture IS too lean and Increase jet size. If
operation improves, continue to increase jet size to
obtain peak performance. If operation becomes
worse, decrease jet size to obtain peak performance.
6. After proper main jet is selected, recheck jet needle
and needle jet.
Carburetion
POWER JET SYSTEM
Principles of Operation
The power jet system is similar to and works in conjunction with the main system.
The power jet system starts to function at engine
speeds of approximately 5000 rpm and above. High
velocity air moving through the venturi, past the power
jet outlet, creates a vacuum to pull fuel through the
power jet and out the outlet. At the same time air is
drawn through the power air jet to mix with and help
atomize fuel from the power jet.
When the power jet system is functioning, it supplies
approximately 40 per cent of the fuel requirement while
the main jet supplies 60 per cent.
POWER
JET_~\l,"""\.\,
\-\~?~~~=1!1
FUEL LINE
M27236
POWER JET
Power jets are available in sizes from number 60 to
number 200. The size number corresponds to flow and
not necessarily to hole size.
NOTE: Never change the power jet by more than one
size at a time.
Make minor changes to both the power jet and main jet
at the same time. Follow the main jet system tuning
procedure for the power jet system.
When experiencing erratic operation or overheating,
check the power jet and power jet outlet for dirt and the
external fuel line for leakage.
The power jet system starts to function at engine
speeds of approximately 5000 rpm and above. High
velocity air moving through the venturi, past the power
jet outlet, creates a vacuum to pull fuel through the
power jet and out the outlet. At the same time air is
drawn through the power air jet to mix with and help
atomize fuel from the power jet.
When the Dower iet svstem is functionino. it suoolies
POWER
JET_~\,,",,,,\.\,
FUEL LINE
\-\~?~~~=1!1
17
18
Carburetion
COMPENSATION FOR ALTITUDE AND TEMPERATURE
An engine loses about 3-1/2 per cent of its power for
each 1000-foot (304.8 m) increase in elevation. Although this power loss cannot be regained, tuning the
carburetor will insure peak performance at operating
altitude . Adjustments to the drive train will also help
improve operation .
At high altitudes or high temperatures, the carburetor
must be tuned for less fuel throughout most of the
throttle range. The following tables provide guidelines
for tuning the carburetor for high altitude. Refer to
pages 24 and 25 for related part numbers .
TRAILFIRE CARBURETION RECOMMENOATIONS *
Temperature
Component
Sea Level to
4000 ft. (1 219 m)
(Factory Installed)
Below OaF (-18°C)
Above OaF (-18°C)
Main Jet
Main Jet
Jet Needle
Needle Jet
Throttle Valve
Pilot Jet
Air Screw
Idle Speed
200
190
6F27-3
166-06
3.0
30
1-1/2 Turns Open
1800-2300 rpm
All Temperatures
4000 ft. (1 219 m)
to
6000 ft. (1 829 m)
6000 ft. (1 829 m)
and
above
190
180
6F27-3
166-06
3.0
30
1-1/2 Turns Open
2000-2500 rpm
170
160
6F27-3
166-06
3.0
30
1-1/2 Turns Open
2000-2500 rpm
TRAILFIRE LX CARBURETION RECOMMENDATIONS *
Temperature
Component
Sea Level to
4000 ft. (1 219 m)
(Factory Installed)
Below OaF (-18°C)
Above OaF (-18°C)
Main Jet
Main Jet
Jet Needle
Needle Jet
Throttle Valve
Pilot Jet
Air Screw
Idle Speed
240
230
6F27-3
166-00
3.5
25
1 Turn Open
1800-2300 rpm
All Temperatures
4000 ft. (1 219 m)
to
6000 ft. (1 829 m)
6000 ft. (1 829 m)
and
above
230
220
6F27-3
166-00
3.5
25
1 Turn Open
2700-3200 rpm
210
200
6F27-3
166-00
3.5
25
1 Turn Open
2700-3200 rpm
*These are suggested carburetor component changes from stock to altitude and temperature requirements. See
pages 2 through 18 and 24 and 25 for explanations and details of optional fine tune components.
OCl~1l
IVVV-IVV~
\.:Jv..... O III) Illlilt::d::>t:: III t::1t::VClllon. Al-
though this power loss cannot be regained , tuning the
carburetor will insure peak performance at operating
altitude . Adjustments to the drive train will also help
improve operation.
At high altitudes or high temperatures, the carburetor
must be tuned for less fuel throughout most of the
throttle range. The follow ing tables provide guidelines
for tuning the carburetor for high altitude. Refer to
Carburetion
19
SPORTFIRE CARBURETION RECOMMENDATIONS*
Temperature
Below
OaF (-18°C}
Above
OaF (-18°C)
All
Temperatures
Component
Sea Level to
4000 ft. (1 219 m)
(Factory Installed)
4000 ft. (1 219 m)
to
6000 ft. (1 829 m)
6000 ft. (1 829 m)
and
above
Main Jet
210
200
180
Main Jet
Power Jet
Jet Needle
Needle Jet
Throttle Valve
Pilot Jet
Air Screw
Idle Speed
200
170
6F27-3
159-00
3.0
25
1-1/2 Turns Open
2400-2700 rpm
190
170
6F27-3
159-00
3.0
25
1-1/2 Turns Open
2600-3000 rpm
170
170
6F27-3
159-00
3.0
25
1-1/2 Turns Open
2600-3000 rpm
*These are suggested carburetor component changes from stock to altitude and temperature requirements. See
pages 2 through 18 and 24 and 25 for explanations and details of optional fine tune components.
L1QUIFIRE CARBURETION RECOMMENDATIONS
TEMPERATURES ABOVE O°F ( -18°C)
Carburetor
Main Jet
Power Jet
PTa Carbo
Mag. Carbo
Jet Needle
Needle Jet
Throttle Valve
Pilot Jet
Air Screw (Turns Open)
Idle Speed (RPM'S)
Sea Level to
4000 ft. (1 219 m)
4000 to 8000 ft.
(1 219 to 2 438 m)
8000 ft. and up
(2438 m)
150
130
100
110
105
6DH22-3
159 (P4)
3.5
40
1-1/2
2000 - 2500
90
85
6DH22-3
159 (P4)
3.5
40
1-1/2
2000 - 2500
85
80
6DH22-3
159 (P4)
3.5
40
1-1/2
2000 - 2500
TEMPERATURES BELOW O°F ( -18°C)
Carburetor
Main Jet
Power Jet
PTa Carbo
Mag. Carbo
Jet Needle
Needle Jet
Throttle Valve
Pilot Jet
Air Screw (Turns Open)
Idle Speed (RPM'S)
Sea Level to
4000 ft. (1 219 m)
4000 to 8000 ft.
(1 219 to 2 438 m)
8000 ft. and up
(2438 m)
160
140
110
115
110
6DH22-3
159 (P4)
3.5
40
1-1/2
2000 - 2500
90
85
6DH22-3
159 (P4)
3.5
40
1-1/2
2000 - 2500
85
80
6DH22-3
159 (P4)
3.5
40
1-1/2
2000 - 2500
tion on page 20 and use the graph
provided to further fine tune your
carburetor.
IMPORTANT: The carburetion recommendations
shown in the LlaUIFIRE charts are
based on general conditions and
will not necessarily provide optimum performance in all operating
'"
I
\
IV'-'l
Above
OaF (-18°C)
All
Temperatures
IVlall.
\,Iv'
Main Jet
Power Jet
Jet Needle
Needle Jet
Throttle Valve
Pilot Jet
Air Screw
IrHo ~nooti
,"' v
,"vv
'vv
200
170
6F27-3
159-00
3.0
25
1-1/2 Turns Open
?AnrL ?7nn rnrn
190
170
6F27-3
159-00
3.0
25
1-1/2 Turns Open
170
170
6F27-3
159-00
3.0
25
1-1/2 Turns Open
?~nn_ ~nnn rnrn
.,~nn_~nnn rnrn
20
Carburetion
Carburetion Explanation
Temperature , altitude and even humidity affect the
amount of oxygen supplied to the engine combustion
chamber . .
Basically, as temperature, altitude and humidity increase, the amount of oxygen in the atmosphere decreases . As oxygen decreases, the amount of fuel
delivered to the engine combustion chamber must be
decreased or a loss of performance will result.
. For example, if you consistently operate the snowmobile at the upper end of the 4000 to 8000-foot (1 219 to
2438 m) range, say 7000 feet (2 134 m) (at temperatures of O°F [ -18°C]), you may wish to install a 120
main jet and leave the 90 and 85 power jets alone.
IMPORTANT: Avoid installing jet sizes that are too
lean (small) as piston seizure may
result.
Normally the number 40 pilot jet will provide good
starting characteristics at the 4000 to 8000-foot (1 219
to 2 438 m) range. In some instances it may be
necessary to richen the pilot system to make up for fuel
that is lost by leaning (reducing main jet size) in the
main carburetor system.
The graph gives an indication of specific jet sizes to be
used at given altitudes and temperature. However,
keep in mind that temperature and humidity levels will
also affect engine output, especially when temperatures are at one extreme or the other.
Many different factors affect snowmobile performance.
To receive ultimate performance from your snowmobile all factors must be considered . Using the base line
jet sizes listed in the chart and the graph, you should
have a good performance level from which to fine tune
your snowmobile.
Basically, as temperature, altitude and humidity increase, the amount of oxygen in the atmosphere decreases. As oxygen decreases, the amount of fuel
delivered to the engine combustion chamber must be
decreased or a loss of performance will result.
. For example, if you consistently operate the snowmobile at the upper end of the 4000 to 8000-foot (1 219 to
2438 m) range, say 7000 feet (2 134 m) (at tempera-
21
Carburetion
CARBURETION GRAPH
160...---..-----..."...-----------------------------,
- - 0° F (-18° C) AND ABOVE
- - - 00F(-180C) AND BELOW
150~---~~-----=~-----------------------1
1401----------~---~------------------l
130~------------~~--~~--------------;
<,
",
LoU
<,
MAIN JET
!::! 120~........
-----------------~---~----I-\---------i
VOl
........
........
....
..,
LoU
........
........
........
........ ........
........
..................
1001-----------..:::::!IIIIo,..,--~r-----'·---------~---~
90~-----------------~~~~--------~
80~-------------------------~~;;:::-----1
o
2
4
6
8
ALTITUDE x 1000
M29254
1401----------~---~-------------------l
1301--------------~~--~~-------------l
<,
LoU
N'I~I'
",
MAIN JET
,,_ .
f\
22
Carburetion
MIXING CHAMBER TOP
THROTTLE VALVE-'~ ~
SPRING
~
JET NEEDLE
NEEDLE VALVE
THROTTLE
VALVE
NEEDLE JET
STABILIZER RING
MAIN JET
r:J
MIXING CHAMBER TOP
,
I
O-IHNr, - ,.,~
I
AIR SCREW
~, ~I
J~
/1
AIR JET
I
Carburetion
~35
\-34
r--------,
\
~
I
:
I
I
9
~(?A
I
I
I
I
~-8
M25231
~-13
c:ssnID
10'
~In-':-""'11
I I
I
o
I
I
I
I
I
L
m-14
/v.qp,
I
I
I
I
\
J
e-16
@-15
I
\
I
O'~\
: 27\ 26
I
II
i- 2829
I
0
L- 1-Top
2-Spring
3-Plate
4-E-Ring
5-Washer
6-Jet Needle
7-Throttle Valve
8-Needle Jet
9-Screw
10-Spring
11-Spring
12-Screw
13-Starter Valve
14-Spring
15-Washer
16-Cap
17-Baffle Plate
18-Needle Valve
.....
19-Float Arm
2Q-Floats
21-Main Jet
22-Machine Screw
23-Float Bowl
24-Power Jet
25-Cap
26-Pin
27-Pilot Jet
28-Needle Jet Holder
29-0-Ring
3o-Gasket
. 31-Clip
32-Plate
33-Tube
34-Washer
35-Machine Screw
36-Washer
Exploded View of Power Jet Carburetor
r--'
I
1/3
I
~_4
I
-6
: '--5
I
I
:A-7
12
23
24
Carburetion
POWER JETS
M25744
§rD
Temp.
Altitude
HOT
HIGH
MAIN JETS
Mikuni
No.
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
155
160
165
170
175
180
185
190
195
200
210
220
230
240
250
260
270
280
290
300
310
320
330
340
350
360
370
380
390
400
410
420
430
440
450
460
470
480
Temp.
Altitude
HOT
HIGH
John
Deere
No.
M66899
M66900
M66901
M66902
M66903
M66904
M66905
M68789
M66906
M68790
M65336
M68791
M65335
M68792
M65332
M68793
M65333
M68013
M65334
M68794
M65468
M68277
M65469
M68795
M65470
M68276
M65471
M65472
M65852
M65882
M65853
M65854
M65855
M65883
M65884
M66324
M66325
M66326
M66327
M66328
M66329
M66330
M66331
M66332
M66333
M66334
M66335
M66336
M66497
M66498
M66500
M66824
M66907
M66908
Temp.
AltItude
Mlkunl
No.
John
Deere
No.
HOT
HIGH
COLD
SEA
LEVEL
60
65
70
75
80
85
95
100
105
110
120
140
145
150
155
160
165
170
175
180
185
190
195
200
M68765
M68766
M68767
M68768
M68769
M68770
M68771
M68772
M68773
M68774
M68775
M68776
M68777
M68778
M68779
M68780
M68781
M68782
M68783
M68784
M68785
M68786
M68787
M68788
RICH
John
Deere
No.
Fuel
Mixture
Fuel
Mixture
LEAN
M25745
Fuel
Mixture
LEAN
PILOT JETS
Temp.
Altltude
Mlkuni
No.
HOT
HIGH
15
17.5
20
22.5
25
27.5
30
~
M22346
4
COLD
M~~~g~
HOT
Mikuni
No.
Deere
No.
Fuel
Mixture
70
75
80
85
90
95
100
105
M66899
M66900
M66901
M66902
M66903
M66904
M66905
M68789
LEAN
M25745
SEA
LEVEL
HIGH
45
50
55
60
60
65
70
75
80
85
95
100
105
110
120
140
M66912
M66913
M66745
M68796
M66929
M68797
M66844
M66914
M65355
M66746
M66663
M66672
M66915
M68765
M68766
M68767
M68768
M68769
M68770
M68771
M68772
M68773
M68774
M68775
M68776
LEAN
RICH
LEAN
Carburetion
THROTIlE VALVES
Mikuni
No.
25
JET NEEDLES
John Deere
Snowmobile and
Part No.
Fuel
Mix.
Trailfire
RICH
Temp.
Altitude
HOT
HIGH
Fuel
Mixt ure
E·Ring
Position
LEAN
M68278
M68279
3.0
3.5
LEAN
0
->
M22341
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Sportfire
M66880
M66881
M66882
M66344
M66743
M66744
M66883
1.5
2.0
2.5
3.0
3.5
Liquifire
M68798
M68799
M68667
M68800
M68801
RICH
!
RICH
M22345
M22344
LEAN
SEA
LEVEL
COLD
NOTE: Throttle valves are not interchangeable between snowmobiles.
RICH
JET NEEDLE PART NO.
NEEDLE JETS
Alti·
tude
Temp.
Mikuni
John
Fuel
Deere No. Mixture
(159)
~
1."--"
~
M22343
•
••
HOT
~
COLD
HIGH
SEA
LEVEL
HOT
HIGH
COLD
SEA
LEVEL
3.0
3.5
P-4
P-6
P-8
0-0
0-2
0-4
M66894
M66741
M66895
M66740
M66896
M66897
LEAN
M68699
M68273
M68698
M68308
•
LEAN
T
LEAN
Soorttire
M22341
0.5
1.0
1.5
2.0
2.5
3.0
M66880
M66881
M66882
M66344
M66743
M66744
6DH3
6DH2
6FL14
6DP1
6DH7
6DP5
6DH8
6F27
6DH22
M65354
M66656
M66422
M66926
M66927
M66941
M67634
M68280
M69074
AIR SCREWS
RICH
M68278
M68279
John Deere Part No.
RICH
(166)
0-6
P-O
0-0
0-2
Mikuni No.
RICH
!
~
Temp.
Altitude
HOT
HIGH
COLD
SEA
LEVEL
M22342
Turns
Open
Fuel
Mixt ure
2-1/2
2
1-1/2
1
1/2
LEAN
RICH
Power Train
The drive train must govern the engine rpm at its peak
power point for maximum performance.
The drive train components are carefully matched at
the factory. In stock applications, except for specific
calibration changes necessary at high altitudes, John
Deere recommends you do not change the power train
components.
Tuning instructions in this section enable you to adjust
the power train shift pattern to agree with the rpm at
which maximum horsepower is delivered. Power train
components which can be tuned are the drive and
driven sheaves, drive sprocket, drive belt, and, on the
UQUIFIRE, the chain tensioner.
IMPORTANT: Use the parts recommended in the
carburetion and clutching charts for
good overall snowmobile performance.
If sharp acceleration is desired a stronger primary
clutch spring may be used to increase clutch engagement rpm's. However, harsh engagement may result
and belt life may be shortened. On some snowmobiles,
top-end performance may be increased by installing
higher gear ratios in the chain case, but, low-end
acceleration may be reduced.
At higher elevations, the decrease in air density reduces the horsepower output of naturally aspirated
engines. Higher elevation also involves deep snow
operation and additional hill climbing.
Because the engine develops less horsepower, the
drive train components and carburetion must be
changed to achieve optimum performance. For exampie; the clutch weights in the TRBOO primary clutch
(L1QUIFIRE) and clutch arms in the 102C primary
clutch (TRAILFIRE and SPORTFIRE) must be of
lighter weight to maintain governed engine rpm's. A
stronger spring in the primary clutch may be used to
increase clutch engagement rpm's and help maintain
governed engine rpm's.
Carburetor parts must also be changed. Because the
engine receives less oxygen at higher elevations, the
fuel flow must be reduced to maintain the orooer
The drive train must govern the engine rpm at its peak
power point for maximum performance.
The drive train components are carefully matched at
the factory. In stock applications, except for specific
calibration channas np.~A~~::Ir\l ::It "'in'" ~ltitl u'foc 'nhn
Power Train
27
DRIVE SPROCKET RATIO
The sprocket ratios are carefully selected after all
operational data is known. Operating rpm, horsepower
curve, clutch ratio, and weight are used to calculate the
sprocket ratio that will produce the best overall performance. Extensive field testing in various snow conditions is conducted before a final selection is made.
The drive and driven sheaves can be matched to the
snowmobile only after the sprocket ratio is determined.
The chart lists available drive sprocket ratios.
NOTE: In some cases where the sprocket ratio is
increased (geared down), peak performance is
obtained by decreasing the spring tension on
the driven sheave (pages 38 and 39). For
example, when changing from a 24/40 to
21/39 gear ratio, change the driven sheave
spring from hole NO.2 to hole No. 1 and see if
performance is improved. In some cases, performance may improve at high altitudes.
AVAILABLE DRIVE SPROCKET RATIOS
Upper
Sprocket
Lower
Sprocket
TRAILFIRE
and
SPORTFIRE
Chain
105
25
(M67970)
39
(M65693)
68
(M66321)
70
(M68634)
NA
103
22
(M68551)
35
(M65809)
NA
66
(M66122)
74
80
99
22/38
71
77
96
24
(M67727)
22
(M68551)
40
(M66804)
38
(M67898)
68
(M66321)
66
(M66122)
70
(M68634)
68
(M66321)
1.77:1
22/39
NA
NA
92
22
(M68551)
39
(M65693)
NA
68
(M66321)
1.86:1
21/39
67
72
88
21
(M66121 )
39
(M65693)
66
(M66122)
68
(M66321)
1.91:1
22/42
NA
NA
86
22
(M68551 )
42
(M65810)
NA
70
(M68634)
1.95:1
20/39
NA
NA
84
20
(M69404)
39
(M65693)
NA
66
(M66122r
2.05:1
19/39
NA
NA
80
19
(M69403)
39
(M65693)
NA
66
(M66122)
2.06:1
17/35
60
65
79
17
(M66302)
35
(M65809)
62
(M66123)
64
(M69026)
2.19:1
16/35
55
60
75
16
lM65811 )
35
lM6580Q)
62
62
(M661?~\
(Mn61?~\
SPORTFIRE and TRAILFIRE
mph at
mph at
7000 rpm
6500 rpm
(Ideal)
(Ideal)
Ratio
Sprockets
UpperILower
1.56:1
25/39
79
86
1.59:1
22/35
NA
1.67:1
24/40
1.72:1
LIQUIFIRE
mph at
8000 rpm
(Ideal) .
::) p rocxe I rano mal WII p roauce me nest overall performance . Extensive field testing in various snow conditions is conducted before a final selection is made.
The drive and driven sheaves can be matched to the
snowmobile only after the sprocket ratio is determined.
The chart lists available drive sprocket ratios.
NOTE: In some cases where the sprocket ratio is
increased (geared down), peak performance is
obtained by decreasina the sorina tension on
LIQUIFIRE
Chain
28
Power Train
102C DRIVE SHEAVE
Principle of Operation
The 102C drive sheave, mounted on the PTO side of
the engine, is a centrifugally-operated clutch.
The drive sheave contains three centrifugal weights
attached by pins to the movable face. As the drive
sheave rotates, these weights provide an outward
centrifugal force . For the clutch to engage, this centrifugal force must overcome the force of the drive sheave
spring which holds the movable face in position. As the
movable face approaches the fixed face , the tension
on the drive belt increases, which starts the snowmobile in motion.
Tuning
When properly tuned, the clutch engagement and shift
pattern will be matched with the engine rpm at which
maximum horsepower is delivered at wide open throttle. This will result in maximum performance . There are
three drive sheave components which may be
changed to modify drive sheave performance: drive
sheave spring, centrifugal weights , and spacer washers.
I I I I I
I I I I I
I I I I I I
~
~
M
HEIGHT
~,
150
(/)
co
~
W
~
o
.J
100
...
,
..J...
~
r;ii~
~
~ .'
. ,, -
~~. ~
~t
L."
~
..::>~
- ':Q'
~
~
Y.
,
~~" ...
1/
-J
The drive sheave spring controls engagement speed. If
a heavier spring' is installed, a higher speed will be
required to overcome the spring force for engagement.
Similarly, if a lighter spring is installed, a lower speed
will be required for engagement.
~
200 - INSTALLED
~
Drive Sheave Spring
,"
/
1'.,0....
~
~
NOTE: With standard weights, heavier springs tend to
cause rough, jack-rabbit starts . Lighter springs
cause smoother starts .
,
_ .~
-,
~
The following table lists the available springs and their
free lengths. The chart shows the required compressing force for each of these springs .
J
.1
FULL
SHIFT
50 ~ ~ 'b-v/
AVAILABLE DRIVE SHEAVE SPRINGS AND FREE LENGTHS
I
I
o
0
II)
('II
I
o
o
o
o,...
COMPRESSED HEIGHT-INCHES
N
o
~
,...
Light
M29255
I
Heavy
Color
Part
Number
Blue
M66024
Brown
M66692
Black
M65684
Silver
M66541
Free
Length
3.000"
(76.2 mm
2.875"
(73.0 mm
3.030"
(77.0 mm
3.475"
(88.3 mm
±
±
±
±
±
±
±
±
0.061/
1.5 mm)
0.06"
1.5 mm)
0.06"
1.5 mm)
0.06"
0.5 mm)
The 102C drive sheave, mounted on the PTO side of
the engine, is a centrifugally-operated clutch.
The drive sheave contains three centrifugal weights
attached by pins to the movable face. As the drive
sheave rotates, these weights provide an outward
centrifugal force . For the clutch to engage, this centrifugal force must overcome the force of the drive sheave
spring which holds the movable face in position. As the
..
.
Power Train
29
Centrifugal Weights·
The centrifugal weights are available in various shapes
and weights. When a lighter weight is installed, the
centrifugal force is less and the clutch takes longer to
upshift. This causes shifting at a higher engine rpm.
The effects of shape are more difficult to understand.
For the standard weight, the total distance that the
weight contacts the rollers during the shift pattern is
about 1-3/16 inches (30.2 mm).
. M25747
M25747
By varying the profile (shape) of the weight, the governed engine rpm and engagement speed can be
increased or decreased. The illustration at right shows
how the weight profile affects engagement speed.
A
Assume, for example, that the ramp of weight (A)
allows the clutch to engage at 3500 rpm. Notice the
point where the movable face roller contacts the steep
incline of the weight.
B
On weight (B), the angle of incline is much steeper,
making it necessary for the engine to develop higher
rpm before engagement takes place. Weight (B) would
therefore provide an engagement speed of more than
3500 rpm.
On weight (C), the angle of incline at engagement is
less than that of weight (A). Because it is easier for
centrifugal force to cause the movable face to move up
ramp of weight (C), the clutch will engage at less than
3500 rpm.
M27238
M27238
I he effects of shape are more difficult to understand .
For the standard weight, the total distance that the
weight contacts the rollers during the shift pattern is
about 1-3/16 inches (30.2 mm).
SHIFT
. M25747
M25747
30
Power Train
102C DRIVE SHEAVE-Continued
The illustration at left shows the profiles and positions
of the same three weights when the clutch has completed its shift pattern.
°
Again note the angles of incline. Assume that the
engine with weight (A) is running at 6500 rpm and is
fully upshifted. The profile of weight (B) is cut back,
providing a smaller angle of incline toward the top. It is
therefore easier for centrifugal force to move the movable face, and engine speed is less than 6500 rpm.
Weight (C) is not cut back as far as weight (A), and
engine speed will therefore be greater than 6500 rpm
for the weight to complete the shift pattern.
The weight kits available are identified in the table
below and illustrated in the drawings on pages 31
through 33.
DRIVE CLUTCH WEIGHTS
KIT NO.
Ught
AM54284*
AM55325
AM54285
AM54286
AM53003
AM54290*
AM54283
AM54282*
AM54287*
AM54288
AM54280
AM53949
AM54920*
AM55159
AM54289
AM54279
AM54281
M27239
M27239
Heavy
*These arms have increased engagement speeds because of flats or notches. They tend to increase slip or
allow the engine to accelerate through a bog area.
These arms will also cause increased belt wear because of additional slip.
,....,"" .."'"".
.......,
~ ... I
... tJU"Lvlll.
Again note the angles of incline. Assume that the
engine with weight (A) is running at 6500 rpm and is
fully upshifted. The profile of weight (B) is cut back,
providing a smaller angle of incline toward the top. It is
therefore easier for centrifugal force to move the movable face, and engine speed is less than 6500 rpm.
,~B
Weight (C) is not cut back as far as weight (A), and
AnninA
~n,u:lrl
\Alill thorofl"\p
O
"
h" ,.......,..+,......... ,..-
~~""
- ---
Power Train
WEIGHT KITS
.246 11 (6.25 mm)
AM53003
M66955(C)(44.7~.5
GRAMS)
M27268
M27271
M66950(K)(54.~.5
GRAMS)
.315 11
.305 11
AM53949
M66947(F)(55.~.5
AM54281
GRAMS)
M27269
M66951(U)(64.~.5
GRAMS)
M27272
.246" (6.25
1l1Tl)===r-
.380" 9.65 nlTl)
.370" 9.40 mm)
AM54279
M66949(R)(59.6+.5 GRAMS)
.24611 (6.25 mm)---J
••,.. r-
t"\
r- '" I u
\ , ",.
n.
,...
~
n " ...,... \
31
32
Power Train
WEIGHT KITS
~_-...-----l
.250" 6.35 mm) _ _T_
. 248" 6.30 nun)
.246"
AM54286
M66957(D)(42.3~.5
M27274
M66953 (B) (44.0:.. 5
GRA1~S)
GRAMS)
M27277
.315"
.305"
M154287
M66878(HE-1)(53.3~.5
GRAMS)
M66954(L)(38.6~.5 GRAMS)
M27278
M27275
4=
I~
.246" (6.25
mm)~
'T_
.250" (6.35 mm) _ _
. 248" 6.30 nun)
d=
i ,--.1T
.315" 8.0nvn)
.305" 7.75 mm)
.246" (6.25 mm)=.T
,.
33
Power Train
WEIGHT KITS
.375"
.380"
.370"
=r-
AM54920
AM54289
M66877(W)(59.~.5
!U6 :l
M68361(HE- 4 ) ( 5 5.~.5
GRAMS)
M27280
GRAMS)
M27282
"127282
"127280
-----.~I-.L
. 246" (6.25111l1)~
.380"
.370 11
AA54290
M66958(HE-3)(45.~.5
AM55is9
M68749(R-l)(57.7~.5
GRAMS)
GRAMS)
M27284
M27281
"127281
"127284
I
.375" (9.52 nm)_..-..J
.380"
.370"
!U6 :l
I
=r-
34
Power Train
CAM ARM
FIXED FACE
SHEAVE
BUSHING (LIQUIFIRE)
/
NUT
,)
,'~CAP
SCREW
~CER
SPIDER
SPRING
COVER
o ;jHER
MOVEABLE
SHEAVE
--7
CAP SCREW
M27289
M27289
Exploded View of 102C Drive Sheave
Spacer Washers
Spacer washers between the shoulder of the fixed face
post and the spider assembly change the position of
the weight's center of gravity. Thi affects the engagement speed and also has some influence on the effective force of the weights .
Removing spacers increases engagement and slightly
increases governed rpm. If using less than two
spacers, check for proper disengagement. Make sure
the movable face contacts the spider assembly in the
hub area with the weights installed .
2 WASHERS
M~~-_~-~
M25754
~.~
~CER
BUTI~
SPIDER
COVER
~NG
Power Train
35
TR800 DRIVE SHEAVE
Principle of Operation
The TR800 drive sheave, mounted on the PTO side of
the engine, is a centrifuga lly-operated clutch.
The drive sheave contains six centrifugal weights attached by pins to the roller arms of the movable face.
As the drive sheave rotates, these weights provide an
outward centrifugal force. For the clutch to engage, this
centrifugal force must overcome the force of the drive
sheave primary spring which holds the movable face in
position. As the movable face approaches the fixed
face, the tension on the drive belt increases and starts
the snowmobile in motion.
Tuning
When properly tuned, clutch engagement and shift
pattern will be matched with the engine rpm at which
maximum horsepower is delivered at wide open throttle. This will result in maximum performance. There are
three drive sheave components which may be
changed to modify drive sheave performance: drive
sheave spring, centrifugal weights and ramps.
Drive Sheave Spring
The drive sheave spring (green) controls engagement
speed. If a heavier spring (red) is installed, a higher
speed will be required to overcome the spring force for
engagement.
250
~
200
I
-l
The following table lists the springs and their free
lengths. The chart shows the required compressing
force for each spring.
PART
COLOR NUMBER
STD. Green M69314
HVY.
lilt: t:llyll
Red
t~,
M69331
t::s d
Rt..\)
W
u
2S
INSTALLED
HEIGHT
150
S?R\~G
GRt..t..~
S?\l.\~G
LL.
FULL -SHIFT -:
100
FREE LENGTH
4.125"
(104.8 mm
4.000"
(1 01.6 mm
±
±
±
±
\';~lllIIIUYClIlY-U~t:1 Cll~U
0.020"
0.508 mm)
0.020"
0.508 mm)
\,;tUl\,;1
r.
The drive sheave contains six centrifugal weights attached by pins to the roller arms of the movable face.
As the drive sheave rotates, these weights provide an
outward centrifugal force. For the clutch to engage, this
centrifugal force must overcome the force of the drive
sheave primary spring which holds the movable face in
position. As the movable face approaches the fixed
face, the tension on the drive belt increases and starts
50
2 .50
I
I
I
I
II I I
I
I
I
I
I
I I I I
2 .00
1.50
1.00
COMPR ESS ED HEI GHT-I NCHES
M292 56
36
Power Train
TR800 DRIVE SHEAVE-Continued
Centrifugal Weights and Ramps
When lighter weights and heavier clutch spring (red)
are installed, the centrifugal force is less and the clutch
takes longer to upshift. This causes shifting at a higher
engine rpm.
For the standard weights, clutch spring (green) and No.
1 ramp, the total angle that the roller arm swings when
the roller travels up the ramp during the shift pattern is
from about 15 to 45 degrees. By varying the weights,
clutch spring and angle of the ramp the governed
engine rpm and engagement speed can be increased.
The shift pattern remains about 15 to 45 degrees. The
illustrations show how centrifugal weights, spring and
ramp angle affects engagement speed.
Assume, for example, that the standard weights, spring
(green) and NO.1 ramp allow the clutch to engage at
approximately 4400 rpm. Notice the point where the
roller contacts the initial angle of the NO.1 ramp.
TR 800 CLUTCH RAMPS
RAMP 1 : 1982 PRODUCTION
RAMP 2 : 1982 HIGH ELEVATION
With lighter weights, heavier spring (red) and No. 2
ramp the engine must develop higher rpm before engagement takes place. Lighter weights, heavier spring
and NO.2 ramp would provide an engagement speed
of approximately 5100 rpm.
M2925 7
When lighter weights and heavier clutch spring (red)
are installed, the centrifugal force is less and the clutch
takes longer to upshift. This causes shifting at a higher
engine rpm.
For the standard weights , clutch spring (green) and No.
1 ramp, the total angle that the roller arm swings when
the roller travels up the ramp during the shift pattern is
from about 15 to 45 degrees. By varying the weights ,
Power Train
37
The illustration shows the position of the roller on the
ramp when the clutch has completed the shift pattern.
IMPORTANT: The angle on the ramps is very critical. DO NOT under any circumstances attempt to alter the ang.le of
the ramps.
DRIVEN SHEAVE
Principles of Operation
The driven sheave works with the drive sheave to
provide a smooth transition from low speed to high
speed ratio.
The driven sheave is torque sensitive. If an increased
load or high torque requirement occurs after snowmobile is up to speed, the cam bracket in the driven
sheave forces the sheave halves together. The snowmobile then travels at a slower speed while maintaining
high engine rpm.
Because the driven sheave can sense load and shift
into the proper ratio, engine rpm remains at peak
output at wide open throttle. If the driven sheave did
not downshift, the engine would run below its maximum power rpm.
me ramps.
M25756
M25756
38
Power Train
DRIVEN SHEAVE-Continued
Tuning
If there is a loss of snowmobile performance or if the
drive belt appears too loose , remove "anti-creep"
shims .from the driven sheave until snowmobile just
starts to "creep" at engine idle speed. Then add one
shim to tighten the drive belt. This holds the belt tighter
in the drive sheave and allows clutch engagement at
the lowest drive ratio.
M25?5?
Driven Sheave Spring
The spring tension determines engine speed during
the shift pattern. Spring tension is adjusted by selecting
one of four numbered holes in the cam.
A
CAUTION: When changing spring tension,
. . be sure governed speed is not exceeded
(pages 43 and 44).
Decreasing spring tension allows the driven sheave to
shift into a higher ratio under the same load and thus
decreases engine speed.
M25758
Decrease spring tension:
-If the engine is operating at speeds above the peak
power curve.
-Under light load conditions, such as a lightly snowcovered lake.
Increasing spring tension prevents the driven sheave
from shifting up and thus increases engine speed.
Increase spring tension:
~ ~f _~~~ ~r.iy~n. ~b~a_~e_i.~_~~.i~LnJ1.ln~o_~ _~i.g.'1~r_cat!,<? ~,h?r,",
drive belt appears too loose, remove "anti-creep"
shims .from the driven sheave until snowmobile just
starts to "creep" at engine idle speed. Then add one
shim to tighten the drive belt. This holds the belt tighter
in the drive sheave and allows clutch engagement at
the lowest drive ratio.
BUSHING
I
BEARING
/
r-,..nr-.,
~
~HEAVE
AND POST
Power Train
Cam Angle
The cam angle works with the spring tension to determine how easily the driven sheave will shift up. If spring
tension remains the same and cam angle is increased,
the driven sheave will shift to a higher ratio under the
same load and will lower the engine rpm. If cam angle
i decreased, engine rpm will increase. For example, a
38° cam angle will provide more engine rpm and shift
up slower than a 44° cam angle .
COMPOUND CAM
PRETENSION CHART
Insert spring tang into
cam hole number-
Place cam and spring over fixed-face
hub with spring tang in hole of fixed
face. Rotate cam clockwise past ramp
indicated.
1
2 (std.)
3
4
- - -- -- - - - - _ .. -
1
1
1
2
_ .• _ -
_. _- -- -;;:1". ' -
ramp
ramp
ramp
ramps
- _ • ••
-'.;;:;1'-
i decreased, engine rpm will increase. For example, a
38° cam angle will provide more engine rpm and shift
up slower than a 44° cam angle.
Degrees of Rotation
to Pass Ramp
50°
80°
110°
140°
Pounds of Spring Tension
Measured at Sheave Rim
5
6
8
10
lb.
lb.
lb.
lb.
(22.2
(26.7
(35.6
(44.5
N)
N)
N)
N)
39
40
Power Train
DRIVE SHEAVE AND DRIVE-N SHEAVE ALIGNMENT
The drive and driven sheaves must be aligned for peak
performance and maximum belt life.
TRAILFIRE and SPORTFIRE
I
------,
I
laD
I
I
I em
'
rml
I
I
aD
I
\
..... -
I
-_/
ROTATE PRIMARY CLUTCH 1200 WHEN
CHECKING ALIGNMENT TO ALLOW
FOR SHEAVE RUNOUT
I
I
J
JDM-81
CLUTCH ALIGNING TOOL
11.47"
1~------~(291.33 n m ) - - - - - - - - _ I
M27286
NOTE: Remove drive belt and driven sheave. Use
JDM-81 Clutch Aligning Tool to make the following adjustments.
Center Distance Alignment
Hub of drive sheave should fit fully into notch in JDM81 Clutch Aligning Tool. If not, loosen engine mounting
bolts and move engine as required.
Driven Sheave Offset Alignment
Rotate drive sheave and check for offset alignment
every 120 degrees (three places). Ears on JDM-81
Clutch Aligning Tool should align with inside of stationary face on drive sheave. If not, add or remove
shims on driven sheave shaft.
Drive Sheave Alignment
Rotate and check drive sheave for alianment everv 120
,....._ •• _
•••• _,._'-'
........ "'"
••• "'-'&"IIIIUIII
'-' 'Cill.
IIlv.
TRAILFIRE and SPORTFIRE
I
------,
laD
'
aD:
Power Train
LIQUIFIRE Driven Sheave Offset
Alignment
NOTE: On the LlQUIFIRE, center distance and drive
sheave alignment cannot be adjusted. Secondary sheave offset is adjustable.
41
L~====:;7
T
A
1. Remove belt.
2. Separate driven sheave and insert 3/8-inch (9.5
mm) keystock. Measure distances A and B every
120 degrees '(three places) on the clutch.
M29259
IMPORTANT: Do not allow the bar stock to contact
the rivet heads securing the driven
sheave to the hub.
3. Use the following formula to calculate offset.
A+B
-2- = OFFSET
4. If offset is not between 1.44 inches (37 mm) to 1.48
inches (38 mm), add or remove spacers from driven
sheave as necessary.
LIQUIFIRE CHAIN TENSIONER ADJUSTMENT
1. Loosen jam nut, and turn adjusting screw in fingertight.
2. Turn the driven sheave 1/2 turn forward, check
adjusting screw again. Turn driven sheave another
1/2 turn and check adjusting screw a second time.
\
3. Back off adjusting screw 1/4 turn, and tighten jam
nut.
M25761
I.
Hemove belt.
2. Separate driven sheave and insert 3/8-inch (9.5
mm) keystock. Measure distances A and B every
120 degrees '(three places) on the clutch.
IMPORTANT: Do not allow the bar stock to contact
the rivet heads securing the driven
sheave to the hub.
3. Use the followina formula to calcLlI~tA ()ff~At
~\
. KEYSTOCK
M29259
42
Power Train
DRIVE BELT DIMENSIONS
The drive belt dimensions are carefully calibrated when
the drive system is matched to the machine at the
factory. Dimensions critical to the performance of the
machine are the outside circumfe rence of the belt and
the width of the belt. Circumference and width both
affect the shifting characteristics of the clutch.
A drive belt that is not to specification will not perform
well. A drive belt that is too long will decrease top
speed and raise engagement speed, and one that is
too short will increase top speed but reduce engagement speed.
A drive belt that is worn affects performance similar to
a long belt. A drive belt worn to less than 1-1/8 inches
(28.6 mm) wide should be replaced .
Snowmobile
Belt No. Outside Circumference
TRAILFIRE M66345 46.3" (1 176 mm)
± 0.12" (3.0 mm)
SPORTFIRE
Width
1-1/4"
(32 mm)
M66345 46.3" (1 176 mm)
± 0.12" (3.0 mm)
1-1/4"
(32 mm)
L1QUIFIRE M69170 46.8" (1 190 mm)
±0.25" (6.4 mm)
1-3/8"
(35 mm)
HIGH ALTITUDE APPLICATION
At higher altitudes , the carburetor must be tuned to
provide peak performance. The drive train must govern
the engine rpm at its peak power point for maximum
performance . This means that after the carburetor is
tuned, the drive train should also be tuned to agree
with the new carburetor performance.
The tables on pages 43 and 44 provide guidelines for
tuning the power train for high altitude operation.
factory. Dimensions critical to the performance of the
machine are the outside circumference of the belt and
the width of the belt. Circumference and width both
affect the shifting characteristics of the clutch.
A drive belt that is not to specification will not perform
well. A drive belt that is too long will decrease top
speed and raise engagement speed, and one that is
too short will increase top speed but reduce engage-
Power Train
43
Clutch Recommendations - TRAILFIRE - 102C Clutch *
Primary Clutch
Secondary Clutch
Chain Case
Clutch
Engagement
(rpm)
Governed
Speed
(rpm)
Spacers in
Clutch
Clutch
Spring
Arm
Kit
Spring
Positon
Cam
Gearing
Sprockets
Chain
(Pitch)
Sea Level
to
4000 Ft.
(0 to 1 219 m)
3600
to
3800
6200
to
6700
2
Silver
AM55159
NO.2
38°
17 Tooth
35 Tooth
62
4000 Ft.
(1 219 m)
and
up
4300
to
4500
6200
to
6700
2
Silver
AM54287
No. 2
Compound
AM55127
17 Tooth
35 Tooth
62
Altitude
Clutching Recommendations - TRAILFIRE LX - 102C Clutch*
Primary Clutch
Secondary Clutch
Chain Case
Clutch
Engagement
(rpm)
Governed
Speed
(rpm)
Spacers in
Clutch
Clutch
Spring
Arm
Kit
Spring
Position
Cam
Gearing
Sprockets
Chain
(Pitch)
Sea Level
to
4000 Ft.
(0 to 1 219 m)
3600
to
3800
6200
to
6700
2
Silver
AM54281
No. 2
44°
21 Tooth
39 Tooth
66
4000 Ft.
(1 219 m)
and
up
3700
to
3900
6200
to
6700
2
Silver
AM54920
No. 2
44°
21 Tooth
39 Tooth
66
Altitude
*These are suggested clutch component changes from stock to altitude requirements. See pages 26 through 42 for
explanations and details of optional fine tune components.
' -r ---'
' -r---,
_._----
-,.. •••• '11'
......
. -_ .._..
-_...
-"._--_.-
Sea Level
to
4000 Ft.
(0 to 1 219 m)
3600
to
3800
6200
to
6700
2
Silver
AM55159
No. 2
38°
17 Tooth
35 Tooth
62
4000 Ft.
(1 219 m)
and
up
4300
to
4500
6200
to
6700
2
Silver
AM54287
No. 2
Compound
AM55127
17 Tooth
35 Tooth
62
----- - -
,_ .•VI.,
44
Power Train
HIGH ALTITUDE APPLICATION-Continued
Clutching Recommendations - SPORTFIRE - 102C Clutch*
Primary Clutch
Secondary Clutch
Chain Case
Clutch
Engagement
(rpm)
Governed
Speed
(rpm)
Spacers in
Clutch
Clutch
Spring
Arm
Kit
Spring
Position
Cam
Gearing
Sprockets
Chain
(Pitch)
Sea Level
to
4000 Ft.
(0 to 1 219 rn)
3800
to
4000
6700
to
7200
2
Silver
AM55195
No. 2
Compound
AM55127
21 Tooth
39 Tooth
66
4000 Ft.
4300
to
4500
Compound
AM55127
21 Tooth
39 Tooth
66
Altitude
(1 219 m)
and
up
6700
to
7200
2
Silver
AM54287
No. 1
Clutching Recommendations - LIQUIFIRE - TR800 Clutch*
Primary Clutch
Altitude
Clutch
Governed Spacers
Engagement
Speed
In
(rpm)
(rpm)
Clutch
Clutch
Spring
Secondary Clutch
Ramp
Kit
Spring
Position
Cam
AM55477
No. 2
44
21 Tooth
39 Tooth
68
3-AM55476
No. 2
3-AM55478 AM55479
No. 2
44
20 Tooth
39 Tooth
66
3-AM55476
No. 2
3-AM55478 AM55479
No. 2
44
19 Tooth
39 Tooth
66
Weight
Kit
Sea Level
to
4000 Ft.
(0 to 1 219 m)
4400
to
4600
8000
to
8200
2
Green
M69314
4000
to
8000 Ft.
(1 219 to 2 438 m)
5100
to
5300
8000
to
8200
2
Red
M69331
8000 Ft.
(2438 m)
and
up
5100
to
5300
8000
to
8200
2
Red
M69331
Chain Case
Gearing
Chain
Sprockets (Pitch)
No. 1
6-AM55476
*These are suggested clutch component changes from stock to altitud requirements. See pages 26 through 42 for
explanations and details of optional fine tune components.
NOTE: In many cases, at altitudes of 4000 to 6000
feet (1 219 to 1 829 m), satisfactory performance can be obtained on the TR800 clutch
by using a green spring (M69314), 20/39
gearing, 66 pitch chain, No. 2 ramps, 3(AM55476) and 3-(AM55478) weights.
,
Altitude
Sea Level
to
4000 Ft.
(0 to 1 219 m)
4000 Ft
-
. --- - · · - -· 1
- --
_._-_ ..
_...-...
----
Clutch
Engagement
(rpm)
Governed
Speed
(rpm)
Spacers in
Clutch
Clutch
Spring
Arm
Kit
Spring
Position
Cam
Gearing
Sprockets
Chain
(Pitch)
3800
to
4000
6700
to
7200
2
Silver
AM55195
No. 2
Compound
AM55127
21 Tooth
39 Tooth
66
.4~nn
f:7nn
45
Suspension
The slide rail suspension system allows the weight to
transfer to the rear during acceleration for better traction and ski lift. The following adjustments are provided
to tune the suspension to the rider:
- Front and rear torsion spring preload
-Ski alignment
-Ski steering control
- Track tension
TORSION SPRING ADJUSTMENT
Before adjusting the front and rear torsion springs, ride
the snowmobile to determine adjustment requirements.
Front and rear torsion spring tension can be adjusted
to suit the weight and riding style of the operator.
Front Torsion Springs
NOTE: In deep snow at high speeds, increased tightening of front torsion springs will help provide
additional ski lift. A deep snow suspension kit
for the LIQU/FIRE is available from your John
Deere dealer.
If the front torsion springs are tightened too much, the
ride will be stiff and the front of the snowmobile will
seem light and lift up when power is applied. Added lift
is fine for deep snow but makes the ride choppy on
rough surfaces. The front torsion spring is not the only
adjustment for ski lift, but it does contribute.
M23799
To reduce the spring tension, turn adjusting nuts
counterclockwise. Be sure that at least 1/2 inch (12.7
mm) of the adjusting screws protrudes through the
nuts.
Rear Torsion Springs
If the suspension bottoms frequently, increase spring
tension. If the ride is stiff, decrease spring tension.
To increase preload, move the springs from the bottom
position to the top position.
The slide rail suspension system allows the weight to
transfer to the rear during acceleration for better traction and ski lift. The following adjustments are provided
to tune the suspension to the rider:
-Front and rear torsion spring preload
-Ski alignment
-Ski steering control
46
Suspension
SKI ALIGNMENT
~
I
1-5/16 11
~ .34mm)
The illustrations at left show the proper positioning of
the skis in relationship to the steering arms, tie rods,
and steering column. To align the skis:
1. Raise the front of sled slightly to remove weight
from skis.
2. Position handlebars straight ahead.
3. Measure distances (A and B) between front and
rear wear rod nuts. The two dimensions should be
equal.
4. If adjustment is necessary, remove exhaust silencer
for access to tie rods.
5. Loosen jam nut on end of tie rod. Rotate tie rod until
skis are parallel, and tighten jam nuts.
IMPORTANT: DO NOT exceed 1-5/16 inches (33.34
mm) between tie rod and center of
tie rod end.
6. To realign handlebars, loosen jam nuts on both
sides of adjuster on drag link. Rotate adjuster until
handlebars are aligned. Tighten jam nuts.
7. After aligning the skis, be sure all jam nuts are tight,
and install exhaust silencer.
TRAILFIRE and SPORTFIRE
-J
1_ 1- 5/1 611
~3.34mm)
~ ......
"""v
III
'VIU .. Vli..,IIltJ
LV
UI'I;;
"L'I;;'I;;IIII~ allll;:),
U~ IVU::S,
and steering column. To align the skis:
1. Raise the front of sled slightly to remove weight
from skis.
2. Position handlebars straight ahead.
3. Measure distances (A and B) between front and
rear wear rod nuts. The two dimensions should be
equal.
Suspension
47
SKI STEERING CONTROL
Adjusting Steering Column (TRAILFIRE
and SPORTFIRE)
1. Remove engine with base.
2. Loosen bracket hardware . Position bracket 0.4 inch
(10.16 mm) above ledge in pan. Tighten hardware.
3. Install engine with base. Tighten hardware .
4. Move steering handlebars full left and full right.
Check steering for smooth operation .
NOTE: Clearance must exist between drag link bolt
head and pan when steering is in a full left turn.
If bolt head hits pan, move bracket up.
Clearance must exist between drag link slotted
nut and engine when steering is in a full right
turn. If slotted nut hits engine, move bracket
down.
M25661
Both clearances should be approximately
equal. Readjust if clearances are obviously
unequal.
TRACK ADJUSTMENTS
Snowmobile
TRAILFIRE
SPORTFIRE
UaUIFIRE
Track
Molded rubber with 29 low profile cleats
Molded rubber with 29 low profile cleats
Molded rubber with replaceable wear clips
Check track tension and alignment frequently. A track
that is too loose causes excessive slap which can
damage the track, tunnel, or slide assembly. A track
that is too loose or too tight requires additional power to
operate .
Adjusting Track
1. Suspend rear of sled .
2. Loosen jam nuts on two track adjusting screws.
3. Tension the track so the dimension between the
bottom of the slide wear bar and inside of track
band is as shown in chart above. Measure this
dimension below lower shock absorber mount.
4.' . Tiohten
iam nuts.
,'l'CIIIVVl:: t::IlYllle Willi
. .
UC1~e.
2. Loosen bracket hardware . Position bracket 0.4 inch
(10.16 mm) above ledge in pan. Tighten hardware.
3. Install engine with base . Tighten hardware.
4. Move steering handlebars full left and full right.
Check steering for smooth operation.
NOTE: Clearance must exist between drag link bolt
Tension
3/8" (9.5 mm) slack max.
3/8" (9.5 mm) slack max.
1/2" (12.7 mm) slack
max .
48
Suspension
TRACK ADJUSTMENTS-Continued
After Adjustment
1. Start engine and idle track slowly so it rotates
several times. Turn off engine and allow track to
coast to a stop. Do not brake.
2. Check alignment by seeing where rear idler wheels
run with respect to drive lugs. The rear idler wheels
should run in center of drive lugs .
3. Look under track and see if slide rail wear strip is
directly in the middle of each slide rail opening on
track.
4. Repeat tensioning procedure if necessary .
:M25764
M25764
NOTE: A track always runs to the loose side. For
proper tensioning , tighten adjusting screw on
loose side. For example, if track is too far to
the left, tighten screw on left side to move track
to the right.
TRACK STUDS
Installing Wear Strips
•
o
Performance can often be improved by adding studs to
the tracks.
NOTE: Wear strips must be added to TRAILFIRE,
SPORTFIRE, and UQUIFIRE snowmobiles
when studs are added to the track.
o
o
o
o
Use only the kit indicated for each snowmo bile. Do not substitute.
AM55180 - TRAILFIRE and SPORTFIRE Wear Strip
Kit
AM55182 - UQUIFIRE Wear Strip Kit
1. Remove seat and fuel tank.
A CAUTION: Gasoline is dangerous. Avoid
. . fire due to smoking or careless maintenance practices.
o
o
2. Remove slide suspension.
3. Install wear strips (see illustration at left).
o
o
NOTE: Drilling holes for wear strips is necessary for
1982 snowmobiles. Install rivets from the top
side of tunnel.
1. Start engine and idle track slowly so it rotates
several times. Turn off engine and allow track to
coast to a stop. Do not brake .
2. Check alignment by seeing where rear idler wheels
run with respect to drive lugs. The rear idler wheels
should run in center of drive lugs .
3. Look under track and see if slide rail wear strip is
directly in the middle of each slide rail ooenino on
Suspension
49
Installing Studs on TRAILFIRE and
SPORTFIRE Snowmobiles
Trail Riding and Normal Snowmobili g
The stud kit should be installed in a staggered pattern,
using the number 4 and number 7 holes in the grouser
bar as shown at right.
M23804
NOTE: All studs are mounted in the center band only.
~.
M23804
Turn snowmobile on its side.
2. Use a cold chisel to remove the number 4 and
number 7 rivets from the grouser bars, using the
pattern at right as a guide.
3. Install stud through rivet hole.
4. Apply a small amount of John Deere Loctite to stud
threads.
5. Place "star" claw over stud, and tighten lock nut
securely.
t
FRONT
M23805
M23805
_
- _. _-
~. _ -
-- -
_
.
- ---._-
- :;:;1.-----
bar as shown at right.
NOTE: All studs are mounted in the center band only.
1. Turn snowmobile on its side.
2. Use a cold chisel to remove the number 4 and
number 7 rivets from the arouser bars. usinn thA
M23804
M23804
50
Suspension
TRACK STUDS-Continued
Lake or Hardpack Running
NOTE: Do not use this pattern for trail riding. Carbide
ski wear rods should be used with this pattern.
The stud kit should be installed in a staggered pattern ,
using the number 9,7,4, and 2 holes in the grouser bar
as shown at left.
M23806
M23806
NOTE: The studs are mounted on each outer band
and the center band.
1. Turn snowmobile on its side.
2. Use a cold chisel to remove the number 9, 7,4, and
2 rivets from the grouser bars, using the pattern at
left as a guide.
3. Install stud through rivet hole.
4. Apply a small amount of John Deere Loctite to stud
threads.
t
FRONT
5. Place "star " claw over stud, and tighten lock nut
securely.
M23807
M23807
2
NOTE: Do not use this pattern for trail riding. Carbide
ski wear rods should be used with this pattern.
The stud kit should be installed in a staggered pattern ,
using the number 9,7,4, and 2 holes in the grouser bar
as shown at left.
M23806
M23806
NOTE: The studs are mounted on each outer band
and the center band.
1
Suspension
Stud Kits for LIQUIFIRE Snowmobiles
Two 18-stud kits and two track patterns are available .
I.
I
I
51
The stud kits are:
AM55177 - Steel Stud Kit
AM55178 - Carbide Stud Kit
•
One stud pattern consists of 18 studs and is used for
normal snowmobiling and trail riding.
The other pattern consists of 36 studs and is used for
hardpack and lake running. Use two like kits for the
36-stud pattern. DO NOT use steel and carbide studs
together.
L
NOTE: Carbide wear rods must be used on the skis
when using the 36-stud pattern.
t
1- 1/8
IMPORTANT : Upper tunnel wear strips must be
installed whenever the track is
studded.
•
11
(28. 6 nun)
I
45° SIDE OF BAR
I
I
\
7/8
II
(22.2 mm)
5-1/ 211
{139.7 mm)
-
1\
T
t'" -
T
I
I
•
M257$6
M25766
18-Stud Pattern
I
•
One stud pattern consists of 18 studs and is used for
normal snowmobiling and trail riding.
The other pattern consists of 36 studs and is used for
hardpack and lake running. Use two like kits for the
36-stud pattern. DO NOT use steel and carbide studs
together.
L
NOTE: Carbide wear rods must be used on the skis
J
•
52
Suspension
TRACK STUDS-Continued
.
I
Installing Studs on LIQUIFIRE Snowmobile
I
•
1. Remove suspension bolts.
2. Turn snowmobile on its side, and swing track and
suspension out.
•
L
3. Drill 5/16-inch (7.9 mm) holes in rubber track, using
appropriate pattern as a guide.. Holes for studs
should be centered between fiberglass rods of
track.
•
NOTE: Holes can be made in track by heating a
5/16-inch (7.9 mm) rod or awl and pushing it
through the track.
•
1
1- 1/8"
(28. 6 mm)
4. Place T-nut on inside of track and washer on outside of track.
•
5. Install stud through washer, and tighten T-nut to
lock stud in place. Do not squash or flatten rubber
track when tightening T-nut. Stud should be at least
flush with T-nut.
I
45° 51 DE OF BAR
"•
~
,
5-1 /2"
6. Put track and suspension back in place, and install
suspension bolts.
•
1
{139.7 mm)
I
•I
7/8 " ---.
{22.2 mm)
t-
-
•
•
M25?6?
M257 67
36-Stud Pattern
Due
•
•
•
1. Remove suspension bolts.
2. Turn snowmobile on its side, and swing track and
suspension out.
3. Drill S/16-inch (7.9 mm) holes in rubber track, using
appropriate pattern as a guide. Holes for studs
should be centered between fiberglass rods of
track.
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