Upgrading a Babetta into a Classic Sports 50cc

Upgrading a Babetta into a Classic Sports 50cc
Upgrading a Babetta into a Classic
Sports 50cc Motorcycle
or the one they should have built!!
The project started with a Mustang or type 555 engine
bought off Gibby "Enterprises" at the 50th Anniversary
National Rally back in 2004. The engine had been
rebuilt but was missing the JIKOV 2917 carb, but had
the neck, and also any of the various gear shift lever
mechanisms that JAWA 50cc bikes used with these
engines. The engine was shipped home along with
the usual Grot Bike Award and sat in the garage for
another day.
Timbo and myself did speculate a "what if we" type
idea of whether or not the little engine would fit into my
son's JAWA type 210 Economy 1 speeder that we had
given to him by Mark DeHora the year before. This
bike went reasonably but was still slow.
Onto August 2004 and at the Netley Marsh Motorcycle
Autojumble, which is always a good place to find all
kinds of JAWAs and CZs including Enduros and
Classic, I spotted a type 225 with cosmetic damage.
Fifteen notes were exchanged and I became the
owner of a type 225 2 speeder. It joined the haul of
JAWAs and a CZ250 twin that the "mob" acquired that
day. It's amazing that John Ambroses’ Renault Traffic
made it out of the field without sinking, what with 5
people, a Raleigh RM (1!!) and numerous JAWAs and
CZs. It was also bloody cramped inside as well.
Luckily nobody farted to add to the suffering!!
Back at Timbo's we nicked the spare gas tank I had
bought for the type 210 and then fired the type 225 up.
Having a kick start was an improvement on the type
210's LPA method of starting.
Soon we were
performing speed trials of one against the other down
the 1/2 mile private road at Trickett's Cross and as
could be expected, the type 225 2 speeder peed all
over the 1 speeder type 210. An added bonus that
when some teenage twat on a Peugeot Speed Fight
Sc**ter thing with a "performance" exhaust challenged
me to a race down the lane, the little JAWA also peed
over that as well, though when the automatic gear box
changed up via neutral and disengaged the drive for a
second, I dropped back and thought that that was as
quick as the little JAWA would go, but when second
gear kicked it I just rocketed on past the sc**ter and
into the distance!!
Back into the garage and modify the baffle / restrictor
and back out again on the lane with John Ambrose
matching speed on the CZ250 which clocked me at 42
MPH eventually.
Bearing in mind that CZ twin
speedos are notorious for reading less than actual
speed by more than 2 or 3 MPH (or 8 MPH in the case
of a speeding ticket I received from a motorcycle cop
back in 1984!! 38 MPH actually, 30 MPH on the
clock!!) Anyhow, quite good going for such a little
engine. The automatic gear change is a novelty in
itself and everyone had a play on it.
Now that I had a possible bike to convert I decided to
go for it and armed with angle grinders and expensive
welders, hammers and hacksaws, etc. the 225 engine
was removed and stuck into the type 210 for obvious
reasons and the Mustang engine bracketed and fitted
in place.
This involved having to turn the frame upside down
and make two across slash cuts and one length ways
into the frame tube belly to allow the pipe to be
hammered flat so that it didn't foul the Mustang
engine's top mounted gear actuator mechanism. This
was TIGed shut and filled in with stick welder. The
original front engine mounts were ground away and
When this was done, still with the frame upside down,
suitable engine front mounts were sourced from the
front mount plate of a dead JAWA type 638 frame,
being of suitable quality proper metal which welded on
nicely after they were bolted into place on the fitted
upside down Mustang engine. Now with the engine
bolted into place on the frame it was turned back onto
its wheels and sat on to see how it felt and if the frame
could be flexed as the engine is a stressed member on
the ZVL type mopeds!! NO it couldn't but it was
discovered that the rear bottom of the mudguard hit
the spark plug when the forks were compressed all the
way (6 cm.). So the mudguard was removed and
luckily the wheel was well clear of the engine.
OK, so now we had a moped with a decent engine that
still looked like a type 225 Babetta with a bigger
engine. Still far cooler than any sc**ter for a 16er to
ride but still lacking style.
Anyone who read the Letters Page in Bike magazine
back in May 2005 will have spotted my star letter that
they titled "Strike Him Out Of The Will!!" on the horrors
of a biker finding that his teenage offspring want to turn
to the dark wimpy side of "motorcycles" and ride
sc**ters!! My son kept stating that he didn't want a
bike with gears and Timbo did point out that maybe the
dark side was luring him. Obviously time to act and
fast, before he starts to use foul language such as
Lam****a and V***a amongst biking company!! I still
reckon that all sc**ter magazines should be kept on
the top shelf away from young impressionables!!
So we have a Babetta with a Mustang engine and it
has Gremica wheels to boot!! Still doesn't look the part
though until I dig up a knackered CZ 125 Cezeta frame
the following week and haul it over to Tibo's place
where we cut off the cross bar and seat rails in one
piece. The rear seat rail spacer was just right to be
welded onto the rear main frame spar where it starts to
turn downwards. The front I cut short and used some
more old JAWA 350 engine mount plates to marry it
up, with heavy welding, to the rear of the headstock
sides. Now it was looking more like a bike!!
Using a CZ cross bar also came with the ignition coil
hanger and strengthened the frame even more. It also
allowed for the fitting of a CZ gas tank which would
give a Mustang engined bike 350.064 miles per full
tank it was worked out. So no late night, "Dad, I'm out
of gas" phone calls or a good excuse to reply, "Well
push it!!".
However a CZ saddle didn't look right on the bike at
the tail end, being too long and also the tail end lights
needed somewhere to live. A CZ Custom Mk.II.
saddle was also far too long.
The months went by and the project was mothballed
usually due to the weather but mainly due to other
bikes to work on. In September this year I had Timbo
flat bed combi the thing over and I started to wire the
thing up and sort out the brakes and gear shift
The saddle and tail lights plus rear end styling problem
was solved by bolting a JAWA TS 350 rear end
plastics and mudguard unit straight onto the saddle
frame rails. It fitted like a glove, almost as if it was
made for it. This solved the tail lights as well. I'd
curtailed the original mudguard up to the rear most of
its mounting lugs so it continued in use but was not
visible from the rear and matched the radius of the
plastic JAWA item over it.
Next the saddle was cut back at the front of the pan a
few inches shorter than one would think obvious so
that the saddle foam snuggly mates up to the rear of
the CZ gastank. The saddle pan is to be bolted to the
frame rails once all the wiring is finished.
The wiring was kept to the Mustang wiring colurs as
much as possible because I was using a brand new
Mustang headlamp bought from George Arnold's bike
shop and I had the diagram available from
jawamoped.com. However, being a a wizard when it
come to automotive wiring, I made a few modern
improvements as the generator puts out next to bugger
all power and I needed to milk it for all it could give and
no waste.
OK from the alternator red and green wires the power
flows into a bridge rectifier (Maplins catalogue very
bottom of the list 4 Ampere item!!) bolted to right hand
CZ part of the frame trimming mount lug (another
bonus of the CZ frame!!) it is important that the minus
out spade connector is not used, as the alternator
earths through the frame and the power output drops
to 4 Volts if one does!! The plus output then feeds into
a Yamaha T80 Townmate 6 Volt transistorised
regulator bolted to the other trimming lug on the left of
the frame. From here the power splits up to feed the
lights and indicators as usual on a Babetta or Mustang
but also it feeds through a fuse into a sealed Gel Pack
6 Volt 10 Amp/Hour battery mounted in a large plastic
project box fixed to the Babetta under saddle rear
frame tube trimming lugs by bolts and washers.
On testing the system it operated the lights happily
either without the battery in line, just on the altenrnator
or just with the battery in line and the engine stopped.
The lights are bright with no battery and just over
tickover revs and stay the same through to peak revs
so I think it works good enough. The bike is running 1
x 25 Watt headlamp and 2 x 4 Watt tail lamps so
apparently I've improved on the Mustang's 30 watts
and the Babetta's 25 Watts somewhat.
All the wiring was done with soldered crimp connectors
using automotive wire. The switch gear on the CZ
handlebars is Cezeta and I used the CZ plug to hook
into the loom I'd built.
The ignition was wired up with the coil also having its
power fed through the handbar kill switch just to be on
the safe side. A good kick on the starter had a literally
cracking spark at the plug. I was unable to measure
the spark's strength using the HOTTAS (Hold On To
This A Second!!) test method as my son had assisted
on another bike spark test with this method before.
With the HOTTAS method of magneto / coil testing
one has to gauge the strength of the spark power from
the reaction and language of the assistant. There is of
course, no immediate hazard or risk to the tester when
using the HOTTAS method, only the assistant, so it is
safe to use.
Not having the correct JIKOV 2917 carb I used a
AMAL 18mm item bought complete from the 2005
Netley Marsh Bike Autojumble for 15 quid.
alluminium soldered the neck manifold piece to an
aluminium plate and drilled and filed a hole through it
to mate up with the bolts and tunneling to the JAWA
neck piece. I then fitted everything back onto the
engine and the bike started up on the first instance of
the push start. (No kick start lever foot piece on the
The AMAL runs a 68 main jet and the manual states
that the Mustang carb also runs a 68 main jet. Luck or
what? As a plus the AMAL has a push down and twist
to lock choke and a tickler. Since fabricating the foot
part for the kickstart lever from a Lucas indicator and
steel sleeving tube, the little engine even starts on one
kick from cold at sub zero temperatures!!
Anyway, back to the carb. The AMAL Tiger Cub
18mm carb has a cotton mesh air cleaner which might
have been OK but for the fact that it faces forwards
within a few inches of the front tyre. Luckily the carb
mouth is a wide 3 inch by 2 inch oval with screw
fittings for the filter unit. I removed this and used a
black project box screwed to the rear of the carb with a
larger hole to feed the air into it. This box is the new
plenum chamber in addition to the normal Babetta
frame tube Plenum chamber and air filter above it.
Anyway a piece of packing foam sprayed with WD40 is
glue gunned across the upper quarter of the box so
that the Plenum area is the other three quarters below
it, giving the engine a suitable resevoir of air and blow
back area for negative back pressure from the exhaust
system (flat spot revs to the layman). From the rear
top of the box a piece of red washing machine hose
feeds up into the normal Babetta frame mounted air
"filter" system. If anyone has seen what passes as an
air filter element in a Babetta, they will understand why
I put "filter" with quote marks. Basically ants could
easily crawl through it.
From then on the air flow and intake is as for the stock
Babetta except that I cut the intake silencer back a bit
by 4 inches to improve the tickover and throttle
response. Connecting up the air system allowed the
engine to settle into a nice smooth tickover once
warmed up.
Onto the exaust system. This is a brand new item,
bought for a fiver, at the Shepton Mallet Bike Auction
and Show in 2004. It is a racing expansion for the now
defunct Aprillia AF50 sports 50cc motorcycle. I had
intended to use only JAWA, CZ and ZVL parts on this
bike but as Aprillia started off in 1969 building CZ type
476 150cc versions of the CZ 125 and also CZ 250
and CZ 350 twins, there is a historical link between CZ
and Aprillia in the past and through the 1970s. I own
an 79,000 mile Aprillia CZ 350 and bloody fast it was
too with its ASSO Werk 14.5:1 compression pistons,
non-Czech mains and other differences to Czech built
machines!! I must return it to the road someday.
The pipe had the neck cut back, eliminating the kill joy
restrictor washer as a bonus, and had a concentric
mounting oval, stick welded on from a salvaged sc**ter
exaust system and this was bolted onto the engine.
The rest of the exaust (and the sc**ter!!) were thrown
away. The midway exaust bracket lug is bolted to a
chrome mudguard brace from a crash damaged type
634 mudguard and this is in turn bolted to the normal
Babetta exaust hanger. The silencer is a 50cc
aftermarket trailbike item and is an aluminium oval
street legal can featuring a flat plate area inside that
feeds through two perforated tubes and into a space
and exits though a 10 degree angled hole. Being a left
hand can on a right hand location, the exaust gases
usefully spray out directly behind the number plate
area. By some stroke of luck the pipe doesn't foul the
centre stand and fits as good as a proper JAWA
factory made system.
For the brake pedal a JAWA 350 brake cross shaft
was used inserted through the swinging arm pivot but
from right to left. The left hand brake switch and side
car brake piece is now on the right. Onto this I welded
a CZ type 476/477/471/472 brake pedal with the hole
part cut off. This was positioned so that it cleared the
underside of the right hand foot rest and the expansion
pipe. A spacer tube was fitted onto the shaft to positon
the pedal clear of everything.
A 1970's CZ rear brake rod was fitted to the back
brake drum and attacted to the brake pedal. Pushing
down on the pedal revealed that it didn't foul the bike
anywhere and now the back brake ability is about 10
times better than when it was on the handlebars. This
location now occupied by the clutch lever of course.
On the left hand side I discovered that a JAWA / CZ
machined tube from somewhere in a twin engine,
happend to fit snuggly over the cross shaft and turns
freely. Also that a JAWA / CZ gear lever interference
fits nicely onto this shaft. A rummage in George
Arnold motorcycles, old JAWA / CZ stores stockpile
revealed a load of J shaped stamped brackets for God
knows what model JAWA / CZ in the past and a brand
new JAWA 90 primary chain, which I bought (in case
Mally or someone wants it!!) and type 555 clutch
pushrods, amongst other things.
These J shaped brackets looked just the job and I
welded one onto the steel sleeve and hooked it up to
the gear shift mechanism on top of the engine. I
positioned the gear lever for best effect and
ergonomics and then welded it into position. So now I
had a bike that changed gear and stopped with a
brake pedal. OK, so the Mustang has a pre-select
type gear box which is a pain if one is used to modern
auto-return boxes but as both Timbo and John
Ambrose have pointed out, my son doesn't know
anything better so it won't be a hastle for him to learn.
The clutch proved to be gummed up and from the
efforts of John Ambrose and myself to put the
microscopic but strong clutch springs back into the
clutch and also fit the circlips utilising a claw hammer
and pin nosed pliers instead of the factory, crowbar
like, spring compression tool, we surmised that the
designer must have been a sadist or something close.
After over an hour of swearing, hunting for shot off
parts, etc. it was all back together again.
It was then that I noticed that clutch pushrod adjuster
on the right in the right hand engine case wasn't
locking when set up. This meant that the bloody clutch
unadjusts itself within 10 seconds of being used. The
end of the screw had been split and broken off
sometime during its history and the lock nut wouldn't
screw onto the thread again. Also the seal leaks in the
case and so I'll have to take it apart and machine up
the broken part. The engine is so torqey that I can just
paddle forwards with the engine running in neutral and
it will smoothly engage first gear or second and pull
away. When the clutch is working for 10 seconds it is
possible to pull away in second gear without slipping
the clutch and with a bit of throttle. The engine runs
smoothly throughout the rev range and has a
noticeable powerband kick in the last thousand RPM
before changing up is required. It goes quite well or
"Bloody Good" as John Ambrose put it and he does
own a couple of FS1Es to compare it with. He rates
the performance as well above FS1E but not as high
as a Puch Grand Prix, which he also owns.
The bike is nice to ride and John Ambrose just loves
the little thing, stopping him test riding it around the
drive takes running out of gas, etc. So he reckons that
I should style the type 210 the same way but leave the
2 Speed engine in it just the same.
Next is fettling the bike up for an MOT test, obtaining a
new registration because the DVLA doesn't keep
records of VIN numbers and what plates go with them,
which is another expensive money making racket
they've dreamt up at DVLA towers. I thought that the
bike just hadn't ever been registered until we tried to
obtain a logbook for another bike that is known to have
been registered locally and lost its number plate in the
past. Nope that one needed re-registering as well and
so 19 quid become 53 quid in one fell swoop. Be
warned about buying bikes with lost number plates!!
And always write the number somewhere on the frame
as you could be somebody's hero in the future.
On the type 210 Jazz I plan to fit a pedal rear brake as
it works better and fit a CZ cross bar, gas tank, JAWA
TS 350 saddle and tail piece plus electrics but that's it.
Oh, and fit a decent electrical system that runs a
battery too.
The overall plan is that the bike will convey my son at
a pace that'll keep up with the Grot Combo to the 2006
National Rally. As the Little Babetta only weighs 100
Pounds I can probally carry it on the Combo hung off
the back. Timbo has proposed a suspended towing rig
arrangement on the Combo. We'll see how it runs on
longer road tests first.
If he does ride it there will there be an award for
furthest distance travelled without having to refuel, as
the 2.89 gallon tank will take the Babetta 350.064
miles in theory. I've worked out that the JAWA Jazz
type 210 with a 2 speeder engine will do 450 miles or
more on 2.89 gallons, so with a JAWA TS 350 4 gallon
tank could the club go for the Lands End to John
O'Groats without refueling unclaimed record?
Anyone interested in converting their unexciting Jazz
or Babetta into a facimile of the classic 1970's sports
moped like our Babetta, feel free to ask for advice. It
wasn't that difficult to build and it seemed to solve itself
when problems arose, unlike the DVLA.
I've received good Construction and Use guidance and
tips on the legal minefields and loopholes from George
Arnold Motorcycles who is an MOT station and both
builds and tests constructed and modified motorcycles
from time to time.
And that's how I did it with and bit of help and
inspiration from friends.
Andy Reid.
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