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OFNA Website
Instruction Manual Z.12R Race
Please read and understand these instructions completely before you install your engine.
Engine Size
Number of ports
Connecting Rod
Power Output*
Useable RPM range*
.12 (2.11ccm)
3+1 (3x transfer-, 1x exhaust-port)
10.0 mm / 7.0 mm bore / SG-shaft
LRP VTEC.12, black anodised
Fully CNC-machined, high-silicium alloy
Fork shaped aluminium using double bushings
Turbo style, LRP Turbo #7 (No. 35170) included
Competition slide carburetor, 5.5mm venturi, lightweight aluminium design
1.45 PS
4.000 – 42.000
*Figures may vary depending on used fuel, muffler and tuning.
Never leave your RC model unattended when the engine is running. If a fault should occur the result could be a
fire in the model which could destroy anything else in the vicinity.
Nitro engines produce gases which are very dangerous for your health; one of them is carbonium monoxide which
can lead to death! Always use your engine outdoors or in well ventilated areas.
Running nitro engines and it’s surroundings get very hot, you can seriously burn yourself when you touch it with
your fingers.
Never try to stop a running engine with your fingers. Please interrupt/pinch the fuel line, or close the top of the
Not suitable for children under 14 years, this engine is not a toy.
Use fresh 2-stroke model car fuel only, never use regular gasoline or airplane fuel! We recommend using our line of
LRP high-quality fuels (16% and 25% nitro). Higher contents decreases your engine’s lifetime, never exceed 30%.
A good airfilter is very important for the life of your engine. Never run without an airfilter, as quick and permanent
damage will result! Don’t forget to impregnate the airfilter with a suitable oil before usage. Replace or carefully clean
the airfilter every 3litres (~1 gallon) of usage.
Use only turbo style glow-plugs for this engine, we recommend using our line of LRP high-quality glow-plugs (availabe
as #6 to #8). Check them frequently and never run with worn-out or old glow-plugs since they could damage your
engine. They turn dull when your engine was too lean and should be replaced, they should stay bright like chrome. If
they are distorted you may have to add a 0.1mm (0.004“) shim underneath the combustion chamber. Whenever you
have trouble with the engine stalling for no reason, replace the glow-plug first!
Never run without a pipe since this will cause excessive overheating and may damage your engine. A proper pipe lets
2-stroke engines run properly and fast. We recommend using our line of LRP high-quality pipes and headers.
We suggest to start with 0.40mm (0.016“) shims underneath the combustion chamber. You may want to adjust the
shims depending on nitro-content (see chart) or track layout. Large tracks may require an extra 0.10mm (0.004“)
shim to reach higher topspeeds, but this will decrease acceleration slightly.
Nitro content
Head clearance
0.40mm / 0.016“
0.50mm / 0.020“
0.55mm / 0.022“
The factory settings of the engine are as following and are a good starting point for you. Turn in the needles completely
(Caution: do not overtighten them!) and loosen them the required number of turns again:
• Mid range:
3 turns
• Main:
2,5 turns
Idle screw (No.1): Adjusts the air flow when
carbureto is fully closed. Turn CW for higher idlespeed and CCW for lower idle-speed. Should be
open 0.5-1.0mm.
Mid range needle (No.2): Adjusts the mid/lowspeed flow rate of the fuel. Turn CW for leaner and
CCW for richer setting.
Main speed needle (No.3): Adjusts the main flow
rate of the fuel (when the throttle is opened
significantly). Turn CW for leaner and CCW for
richer setting.
This is a very important step in ensuring that you get the highest performance and lifetime of your engine, take your
time for proper run-in. We do not recommend using run-in benches, use your car for run-in and use the same fuel as
you will be using for the life of the engine. If your engine doesn’t start easily you may try loosen the glow-plug by ½turn to decompress the engine and try again, don’t forget to tighten the glow-plug again once it started!
• Start the engine and set the main-needle very rich, i.e. excessive smoke coming from the muffler.
• Let the engine idle for 2mins first to warm it up.
• Now start driving your car, it will be slow and sluggish, but this is an important step.
• Do not allow the engine to rev-up too high, run the engine at half speed on the straightaway.
• The engine should not be too cold and not too hot during run-in, 70-90°C (160-195°F) is perfect.
• Let the engine cool down for 15mins after each tank during the run-in period.
• We recommend doing so for 4 tanks of fuel before you start tuning your engine.
It never hurts to have the mixture too rich, but NEVER let the mixture get too lean. Always tune from rich to lean. If in
doubt, richen it up first! Never try to tune a cold engine, run 5 full laps to get the engine up to running temperature
before doing any adjustments!
Basic tuning procedure is as follows:
1. Set the engine’s idle speed up slightly higher than normal.
2. Start tuning your engine with the settings too rich.
3. Always tune main-speed needle (top-end) first.
4. Tune mid-range needle next.
5. Reset idle speed screw.
1. Set the idle speed so your engine doesn’t stall (slightly higher then normal).
2. Go to the track with the main-needle set too rich, there should be heavy smoke coming from the muffler now.
3. Tune the engine by leaning the main-needle 1/8 turn at a time.
Æ Your goal will be that the engine will just reach maximum RPM on the straightaway.
Æ Open the main-needle again by an 1/8 turn when you have reached that point, this should be the perfect
setting for the main-needle (temperature of 95-110°C / 200-230°F).
Æ If the main-needle is set too lean, the engine will overheat and will not accelerate smoothly. If this happens,
immediately stop the engine and richen the main-needle (counterclockwise) 1/4 turn before a new attempt.
4. Adjust the mid-range needle now. Run 3 full laps, stop the car near you and let it idle for 5secs. "Push off"...
It should have slightly richened up, but still accelerate quickly. If it died before the 5secs, check the following:
Æ If it seemed to load up and slowly stop, the mid-range needle is too rich.
Æ If the idle-speed increased before it stopped, the mid-range needle is too lean.
5. You may have to re-adjust the idle-speed now. If it idles too high, the clutch may not release completely and you
will lose "snap" off the corners. If it idles too low, it may stall at the start, or at the end of the straightaway when
you release the throttle.
Ways to measure the engines temperature:
• Temperature gauge method: Pull in quickly and immediately take a temperature reading. Place the gauge
directly over the engine pointed at the glow plug.
• Spit method: Pull in quickly and immediately put some spit on the engine’s head. The saliva should just slowly
boil off (2-3secs). It should not dance around as if it were on a hot griddle, nor should it lay there and steam.
Use after-run oil to keep everything lubricated after you have finished your day. After-run oil helps for an easy start
the next time and protects your internals against rust. Use only "after-run oil" specially formulated for R/C engines. Do
not use silicone shock oil or similar as they will seriously harm your engine.
First let the tank run completely empty at idle until it runs out of fuel (try re-starting it several times), next put a few
drops down the open carburetor and a few drops down the glow plug hole. Spin it over for 5 seconds on the starter box
and you are done.
Treat your engine with care and check it frequently. This engine will rev up to 40'000 RPM and any fault at such high
RPM can cause serious damage. All moving parts inside the engine are subject to wear, you must know if a
piston/liner/conrod has worn out and if they need to be replaced. If you replace one part, please check if everything
else is still in good shape at the same time. If you only change one part and other parts are in bad shape, there’s the
possibility that there will be a new failure soon!
Some important matters:
• Clean the outside of the engine properly before you open it. Any dust or dirt which gets into the engine could
make considerable damage.
• Check the conrod frequently. If you want to replace the conrod, be sure the big end of your crankshaft is still
round and at a good size. If not, also replace the crankshaft.
• When you start putting your engine back together, make sure that each part is totally clean before installation and
please use some oil (after-run is suited well) to lubricate everything.
• Be careful that each part has its correct direction, especially piston/liner/conrod. Both the lower part of the piston
and the lubrication hole in the conrod should be facing to the front (direction to the carburetor).
• Before you install the combustion chamber, please doublecheck that you installed all head shims.
• Use a hex wrench to install the screws. When you start to feel resistance, stop turning the screw. Repeat this for
each screw, use the star-technique to tighten all the screws completely. Do not overtighten them!
Engine does not start
Glow plug defective
Glow plug does not work properly
replace glow plug
check the condition of the glow plug
check the glow plug igniter
check carburetor settings, repeat tuning procedure
unscrew the glow plug completely and use startbox for 5sec
check carburetor setting, repeat tuning procedure
check the fuel line for possible damage
check the carburetor setting
replace glow plug
replace fuel by fresh and correct type of fuel
check the carburetor setting, repeat tuning procedure
clean fuel line, clean & check carburetor
replace fuel line
tighten glow plug and/or cooling head
clean or replace air filter
check the carburetor setting, repeat tuning procedure
replace the glow plug by a correct type
run-in process is not completed
check number of shims
open mid-range needle ¼ turn at a time and re-adjust idle-speed
set idle speed lower
use glow plug with higher number (e.g. go from 6 to 7)
check number of shims
Engine is set too rich
(too much fuel, hits back)
Engine is too lean
(too little fuel, does not start)
Engine doesn’t suck in the fuel
Engine stops after a short time
after glow plug igniter has
been disconnected
Glow plug defective
Bad fuel
Bad carburetor setting
Dirt in fuel line or carburetor
Fuel line damaged
Loose glow plug or cooling head
Air filter old or dirty
Performance decreases after
reaching operating
temperature or engine stalls
from time to time
Engine is set too lean
Glow plug defective or wrong type
Engine runs too hot
Shims under comb. chamber wrong
Bad carburetor setting
Engine’s still keeps running at
high RPM for a moment when
you release the throttle
Glow plug, wrong type (too hot)
Shims under comb. chamber wrong
Please always check www.lrp-electronic.de for guidance if you are experiencing problems!
Please check spare parts availability at www.lrp-electronic.de
All products from LRP electronic (hereinafter called “LRP”) are
manufactured according to the highest quality standards. LRP
guarantees this product to be free from defects in materials or
workmanship for 90 days from the original date of purchase
verified by sales receipt. This limited warranty doesn’t cover
defects, which are a result of normal wear, misuse or improper
maintenance. This applies on:
Engine disassembly by customer
Any modification of the engine done by the
Rust inside the engine
Dust or dirt inside the engine
Damaged engine due to glow plug failure
Scratches inside the engine caused by dirt or dust
Water in fuel
Wrong break-in procedure
Damaged piston due to piston stop devices
Damaged cylinder exhaust port due to piston stop
Breakages at high rpm without engine load
Did not read Instruction manual
In case of problems first check all other components and the
trouble shooting guide, to eliminate all other possibilities or
improper handling. Please only return the sole engine without
the clutch, motor stands, etc.. You can send defective products
to your national LRP-distributor. Hobby shops are not authorized
to replace products thought to be defective.
The original sales receipt including date of purchase needs to be
included. Otherwise, no limited warranty can be granted. For
quick repair- and return service, add your address and detailed
description of the malfunction. Products sent in for repair that
operate perfect will be charged with a service fee. Therefore first
check with the trouble shooting guide.
Our limited warranty liability shall be limited to repairing the
unit to our original specifications. In no case shall our liability
exceed the original cost of this unit. Because we don’t have
control over the installation or use of this product, we can't
accept any liability for any damages resulting from using this
product. By installing or operating this product, the user accepts
all resulting liability.
The specifications like weight, size and others should be seen as
guide values. Due to ongoing technical improvements, which are
done in the interest of the product, LRP does not take any
responsibility for the accuracy of these specs.
Package your product carefully.
Send parcel to your national LRP distributor.
Distributor repairs or exchanges the product.
Shipment back to you usually by COD (cash on
delivery), but this is subject to your national LRP
distributor's general policy.
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