i need help with dropping compression

i bought a 784 kit off e-bay and it was "subposed" to be a 10:25 to 1 kit.
after i got the rings, they told me it was a 12.5:1 kit
i can't fly cut the pistons.
how thick of a base gasket do i need to make it 10.25:1? i want to finish this bike this year!

I have heard of people using two gaskets to drop the compression, but I am not that big of a fan of that

does ape make a bottem spacer for 650?

No

time for race gas.

Computer says 44Thou to get back to 10.25. Cometic will prob cut you one.

What sort of kit was it ? I would think a 12.5 would be rare . Having said that I have had the same thing happen on a H*nda CB985 kit I solved the problem by putting a CB1100 head on. For a short time Wiseco made a Pro Series piston for some bikes with higher comp.

Chris

What is the cranking compression? You can still use 93 octane up to 205 psi, 94 octane can go to 210.
I say put it together and see what you have before trying to fix what your not too sure of. You might end up with 200 psi on cranking compresion and you'll be fine on pump gas.
If you want to lower compresion you can also do it with longer duration cams that close the intake valve later in the rotation.
Or you can retard your intake cam a little :dry:

I have just got done rebuilding my 1987 Warrior with a 10.5 to one piston. Every body said I have to use race fuel and I told them about cranking compression and they looked at me like I was stupid but I did it any way. Hell I even kept the stock cam in there to get more compresion. Stock compresion on a Warrior is 125psi I have now 205psi and run it on 93 octane with no problems. Now this engine has a big one bore piston, you have 4 smaller bores. I think you will be fine, just add a oil cooler because with more compression you will have more heat.