Crankshaft woodruff key

The vespa ive just rebuilt is eating woodruff keys like no ones busness.Anyone had this problem ? If so anty tips on how to stop it [:rolleyes:]

Assuming both the crank and flywheel keyways are fine , then it either not setting flywheel to proper torque or old/poor quality or wrong sized woodruffs


just red your prob.

Most of the time is a question, as said by avenger, of not tighting enough the flywheel nut.
It is not the woodrruff key that keep the flywheel but the conic relation between flywhheel and cranckshaft conic side. They have to form a tight enogh match.

You could lap the flywheel to the crank taper.

This involves removing the woodruff key and applying a small amount of fine grinding paste to the crank taper (It’s easier if you remove the stator plate but remember the position!)

Then place the flywheel on the crank taper and rotate it backwards and forwards, do this several times then take the flywheel off slightly turn it through 90 degrees, re-seat it on the taper and repeat.

If you do this a couple of times then remove the flywheel and wipe the taper clean you should see a matt grey area, this is the contact area between the flywheel and the crank once this is even you can give it a good clean and re-assemble. You are only removing a very small amount of metal so don’t go too mad!

Make sure you clean all of the grinding paste off and don’t get it near the oil seal.

Hope this helps.


Many thanx for your help guys.I made a flywheel holder & tightend the flywheel corectly with a new key.Result everthing is cool[:D] Just a problem with slow response to throttle.Ive moved the stater 1 degree each way to no avail,any ideas[:dance1:]