Scooterotica

Yeah know its not the best solution but I've a SX200 thin taper crank in good condition which I want to use in a very mild 175 conversion (standard pipe, 22mm delly carb etc) Now I know the best logic would be to buy a GP crank for such a thing but sadly I can't afford to ( not made of money plus other commitments dictate) the LI/SX crank is prone to shearing off the odd taper but I've noticed a few peeps getting around this problem by lightening the flywheel. Now does anyone know the standard weight of a ally Ducati 6 volt SX flywheel, what would be a sensible minimum weight to reduce it by which isn't going to effect the tick over etc too much and who could do this job well? cheers Paul

before you do anything, ask yourself how many "thin taper" cranks have actually broken.

I've had scooters since 1968 and the only flywheel/ taper problem I've ever had was a flywheel on a TV200 which split along its taper due to excessive tightening. (air gun in a garage!!)

I know Innocenti revamped the flywheel set up on the GP range to counteract breakages, but with a mild 175 tune, I really don't think its going to be a problem in your case.

Also, beware of replacing good original Innocenti stuff for poor replacement stuff.......theres enough horror stories about poorly fitting parts to last a lifetime.

Lightening may be a good idea but you may sacrifice a smooth tick over due to lack of inertia.

Chris

Thanks for the information and your experience Chris, I've done quite a bit of research on here and the LCGB forum about li/sx crankshafts shearing at the taper. it seems about a 50/50 split to if the crank is suitable/unsuitable for the task- I was thinking about lightening the flywheel just to sit on the fence will probably run the crank and flywheel as the factory intended.cheers again Paul

no problem Paul.

FWIW I ran a TV175 S3 with a Muggy kit on original crank AND 6v points- never missed a beat and no problems.

If you do get the F/W lightened, please advise how it runs- may consider it myself.

Now- time for bedy byes!!

C

If the crank has had a hard life then maybe it could be a problem.
Back in the day, I never heard of it happening - maybe to real racers, but not us street boys.
In '67 my SX had a 70mm bore and tune by A Francis in Watford. Only downside was the huge fuel consumption from the Wal Phillips "fuel injector".

Easiest would be to get the brass centered Ducati flywheel and remove the fan then fit a nylon one, that's what we did in the 80's

dont lighten the cast ducati dont fit a self destruct brass jobby

Muppet wrote:dont lighten the cast ducati dont fit a self destruct brass jobby

Ok so the ally and brass flywheels are a bit of a no-no, what would you recommend ?

warts wrote:If the crank has had a hard life then maybe it could be a problem.
Back in the day, I never heard of it happening - maybe to real racers, but not us street boys.
In '67 my SX had a 70mm bore and tune by A Francis in Watford. Only downside was the huge fuel consumption from the Wal Phillips "fuel injector".

The cranks no shiny NOS item, but had Al Diablo check it out a couple of years ago and he said it was fine, its looking like I'm probably going to run it as is. I've ran a smallframe vespa engine with a small taper (not the thicker PKXL taper) and a lightened flywheel and that helped with the problem of sheared tapers. I was hoping to do similar with the SX crank but not want to remove too much material that it either weakens the flywheel or causes erratic tick-over problems. What's the difference in weight between the standard ally Ducati 6 volt flywheel and the electronic flywheel (using a sx.li cam) ? a lot of people seem to use them on their engines and didn't know if there was a weight difference between them? Paul

there is a comprehensive article about flywheels and lightening in one of Mr B's articles . It gives weights and types of flywheel swopping around etc and replacing the fins with plastic etc .
Most damage on scoots and bikes is caused by over-tightening and heavyhandidness with aluminium .Some people just have no 'feel' with materials