Topic: Performance kits

[smashme33]

 I was wondering if anybody knows where to obtain a performance kit for a 1980 CB650 that contains oversize pistons, rings, and all that hoo-ha. I think Action Fours made them a long time ago, and I can't think of another company that would make them. I realize that the aftermarket has kind of always been limited for this model bike.

[Pinhead]

If you find them, let me know. I've got a '79 CB650 that I'm looking to work on.

That being said, couldn't we just find pistons that match the bore we need? The only other variable is the height above the wristpin, right? As long as they provide decent compression while not interfering with the valves they should work, right? Someone correct me if I'm wrong.

[volz1fsu]

You might try the 750 pistons.  They work for the 550 big bore, same pin height and all.  You just have to cut the right valve reliefs into the tops as long as you don't have the higher dome F pistons.  I would imagine that the 650 has the same pin height as the 750 because the 550 does.  You could even try to fit the 836 pistons if you change to thicker sleeves, all depends on how much time and money you have.