Re: Just set up a new lower engine, and now the rear wheel locks when clutch is engag
The stroke means the distance the piston travels from tdc to bdc, a 66cc engine has a 38mm travel or stroke the 69cc has a 40mm travel or stroke. MBR and Dax both supply 40mm stroke lowers. Since you are comparing the new piston to a piston that has never run on this engine dax will have to tell what you need. Did you take the head off and see if the piston comes out of the cylinder?
Your results may not be the same,Greg