gs 650 bigger valves?

[2v0]

Does anyone know or has anyone put larger intake and exhaust valves in the 81-82 650 head? Trying to get a few more horsepower out of my AHRMA vintage superbike. Thanks J.

[SqDancerLynn1]

I would spend the money to bump the compression up, Light cut from head & barrels, degree the cams. maybe port the head.

[duaneage]

Larger valves are the same as more lift from a flow perspective. Cutting larger valves in can be risky, you have to understand the cooling requirements. You might be able to find someone to regrind a cam for you with more lift or duration and then work on the carbs and exhaust to make the most of it. Any increase in lift, whether from larger valves or more cam, is going to need an increase in compression to take advantage of the change.

The end result would be more power most likely at higher rpm with a decrease in low end power. If that's OK and your willing to spend a lot of time and money getting it right , then go for it.

I would look for a larger bike and move up that way but if there is a class restriction your in or if this machine tickles your fancy take the mod route.

[2v0]

Can't go larger, class limit on displacement. Understand the dynamics of head work, will flow the head before port work. Just wondered if anyone had done the larger valve route. Thanks for your input. J.

[duaneage]

I thought you were up against a class limit.

[2v0]

The limit is on engine displacement, not valve size.