Yes,

All I did change is the ignition side, direct swap, removed the 350 and installed the 250.  The engine is still amazing even with about half the flywheel  weight it will still lug way down and its zippy when revved up.  My riding buddy has been a Bultaco guy since the early 70's and we also swapped his and he couldn't believe how much better his stock 199A rides.  Even with the 250 flywheel I can chug around at an idle no problem...no throttle.

 

Good Luck,

SB

Anyone tried machining the clutch side weight down ? I've machined one down but not tried it yet, I have been told you have to lighten the flywheel as well, apparently there is a formula to follow ??

 

 

 

Edited September 19, 20169 yr by taff_d

If I recall correctly the primary drive flywheel is made of hardened steel, so I'd imaging it's next to imposible to machine.

If you really want to, it is possible to calculate how much a difference a given change in flywheel arrangement will make to the total "flywheel effect".

This will involve working out the total flywheel effect for the crankshaft (all 5 flywheels in the case of a Sherpa T) and the clutch and comparing it with the calculated flywheel effect after making the proposed changes.

 

In the case of the machined-down drive side flywheels in taff_d's photo, I suggest if someone wants to reduce the flywheel effect, only machine the wheels narrower rather than reduce both their width and diameter. This will give you a much bigger (gravity) weight loss for a given reduction in flywheel effect.

As for the question of there being a need to remove mass from both ends of the shaft, it makes no difference to flywheel effect which end of the crankshaft the mass is removed from.

It will however cause the bike to balance a tiny bit off vertical if you only remove mass from one end of the crankshaft

If I recall correctly the primary drive flywheel is made of hardened steel, so I'd imaging it's next to imposible to machine.