willy
XS650 Member
if i remember correctly it was bored out 81 mm pistons, yep and it ran perfectly on stock carbs and jets, ................
I agree with one member on here with the porting and polishing. That watch what you take off cuz yes these ports are definetly large enough compaired to the size of the valve. I've found in my experiences that wether it be a car or snowmobile or bike any motor that the simplest thing you can do is first get in there and smooth out the bends. Don't take to much off just smooth it out. Then the most important part most people overlook is "port matching". You want to have the exact same size hole on the engine side and manifold. Easiest way to do this is place just the gasket or mounting clamp on without the exaust pipes or carbs use a marker to color in what part of the port is smaller or larger than the gasket and grind that down. The objective is too have a smooth flow from engine to exhaust. You can gain good power just from this by eliminating flow resistance.
I finally found Rogers 70hp dyno runs, his mile motor.