Claying motor for clearance/pistons/valves

Hey gang-I am going to bite the bullet and test clay my new 810 for clearance this weekend. My bike mechanic buddy can't watch over my shoulder so I am gonna do it myself. Shouldn't be a problem since I have rebuilt and re-assembled car and bike motors before.

My question is this (since I have never clayed pistons before) what should be the clearance? I figure if I have 1-2 mm. when turning the motor over with a wrench, this should be fine. I want the clearances tight, but obviously not making contact. If I put a 3 mm claying to each piston, this should be enough-correct?

The motor is a '77 Kz650 base, bored Kz750 jugs, 810 Wiseco pistons (10.25 to 1 ratio), Kz750 head gasket, Kz650 head milled 6 thou to clean up the combustion chamber ring, Kz750 cams, Kz 750 intake valves trimmed 15 thou, enlarged 650 intake seats, Gpz 750 springs and I am using the stock '77 650 roller chain. The 650's sprockets have been swapped onto the 750 cams.

Another bike mechanic buddy of mine who races a Kz 900 and a Kz650 took a look at the head surface and valve/seat depression and said I should be ok. I would rather confirm this fact than learn it the first time I buzz the 810 past 9 grand.

Any comments would be appreciated.

Cheers-Colin Firth-Ontario Canada

I have do that on a lot of race motors, never on a bike, one thing to watch is not to put too much clay in there you can bend a valve easy. the best gains will be seen if you degree the cams in

With stock KZ750 cams there is no way that the valves are going to hit the pistons (as long as the cam timing is right and you keep it under 11k rpm) with just an 810 kit.

I know that many people shave .030 off the head on the GPz750's when installing an 810 kit, and I have never heard or read of a valve/piston interference problem.

The geometry of the 750 and 650 is the same, same distance from the crank centerline to the valve face, same stroke, etc.

If you want to use clay to check for yourself (for the learning experience or whatever reason) feel free to do so, but you are safe anyway.

General rule of thumb for safe clearance is .080" on the intake and .100" on the exhaust.
Never hurts to have more though

If you have Wiseco pistons and stock cams, you are wasting your time. You will have much more clearance than you need.

Jay

Thanks Steve and Jay. You guys were two of the brains I was hoping to pick on this topic. You just saved me an afternoon's work.

Colin Firth-Ontario Canada

Post edited by: reborn650, at: 2006/05/19 22:23