Modern Vespa

It happened again, I rebuilt a friends Stella engine with a mazz long stroke crank, and the autostart flywheel won't fit on the crank cone without pinching up against the engine case when torqued.

This had me pull out my calipers and start measuring the original LML cranks in comparison to new mazz cranks that I have lying around waiting to go into an engine.

The fly side cone/stub? is effectively the same length from the web to the end of the cone. The only thing I can find that may be an inclination as to why these new non LML cranks don't work with the original LML autostart flywheel is the depth of the fly side cone threading. I am not positive, but I think this means the cone has the same angle to fit the flywheel, but the cone itself sits further out on the total length of the stub on the LML, while sits slightly closer to the web on the non LML cranks. This would move the flywheel a millimeter or so inward on the non LML cranks.. and cause the LML flywheel with autostart ring to contact case. I can't be 100% sure because when I tried to measure the rest of the stubs minus the threading, my measurements are slightly innacurate on the LML due to the fact that I don't have the tool to remove the inner bearing ring off the stub, so when I used my calipers I had to slightly angle the caliper to reach over the bearing ring while still having the caliper tongue line up with the desired measuring spot at the start of the threading. So my measurements of threading + stub minus threading for each do not equal each other, despite my single measurements of the stub from web to end of stub being equal within margin of error.

The LML crank has a nut threading at the end of the cone which is approx. 14.30mm deep.

The mazz crank has a nut threading at the end of the cone which is approx. 15.18mm.


This is all in my search to understand why two different cranks, both compatible with LML and Piaggo p range cases can create an incompatibility issue with the LML autostart flywheel. But this leads me to trying to find a non LML autostart flywheel that will work on the LML cases with non LML crankshafts. There are later P range models that had autostart flywheels made by Vespa, so I know it should work. Question remains though if using any of the other available autostart flywheels would work on the LML? And my measurements were in search of any specifics that I could possibly look for on other available products to make sure it would work on the LML before purchasing.

I've found these other non LML autostart flywheels:

Piaggio PX80-150 Elestart
https://www.scooter-center.com/en/flywheel-piaggio-vespa-px80-px125-px150-elestart-1794993?number=1794993

Piaggio PX200/Cosa200 Elestart
https://www.scooter-center.com/en/flywheel-piaggio-2300g-2100g-without-sprocket-vespa-px200-elestart-cosa200-elestart-7320021?number=7320021

Sip PX80-200 E Lusso/Cosa
https://www.sip-scootershop.com/en/product/flywheel-sip-touren_51002000

Had the exact same issue with a Pinasco crank on a Cosa 200 motor and an original Ducati PX flywheel. I machined the inside lip of the flywheel and it worked fine...