Okay I was wondering if there is a calculation to findout the exact comp ratio for my motor. I have had the heads milled 10,000ths and the pistons I have are a 9.9 to 1 ratio for a 64 cc head. So can anyone tell me the compression ratio for my motor and what the stock ratio is?

 

You need to know the following to get close.

bore
stroke
piston dome/dish volume
combustion chamber volume

To be more accurate, you need all the variables listed here: http://www.rosspistons.thinkhost.com/calculator.php (it's best to calculate gasket volume using the compressed thickness and gasket bore).

Rich