[pete]

Originally Posted by jimjr21

There are clearances from crankshaft and rod assembly to the surrounding case. These clearances have to be maintained.
So if you have a 24mm crank pin stock and switch to a 22mm pin. Keep the thickness of rod the same and the outside location of the pin the same the center line of the crank pin will move to a 2mm larger circle. Presto +2mm stroke.
Now clearances to head must be maintained. So you need a -1mm rod length center to center. But the real clearance issue happens at BDC where now the piston is 2mm further towards the crank and case. This is why sometimes you see spacer plates put into stroker kits to clearance piston to crank issues. But then you run into cam timing and cam chain length issues. Other ways around it are pistons with different pin heights to compensate with using a crank and rod setup that has pin in higher location than stock.

So you are increassing the distance between main & big end centres... Correct?
A bit more involved than a "smaller Dia crank pin" that was stated in the earlyer post..

Not hard to sorce con rod blanks to machine what ever length rod you require..

I have built complete cranks for Jawa / Westlake & GM speedway motors