1996 Ski-Doo Mach 1 - 670 cc engine .   The modified  hi-performance motor includes:

New PTO end of crankshaft. 

All new crankshaft bearings,rod bearings, wrist pins,and seals.

Crankshaft welded.

Cylinders bored out 1mm oversize.

Wiesco 79mm Pistons

New connecting rods.

Carbon Fiber 155 deg Rotary valve

Cylinder head ground to increase compression ratio.