Changing compression ratio

1958 Views 2 Replies 3 Participants Last post by GRock, Dec 31, 2005

csa98271

Discussion Starter · Dec 31, 2005

Hello
Is it OK to use a thicker head gasket to lower the compression ratio in a TC engine? I have a kit that says with a 85cc combustion chamber and .040 head gasket the c/r will be 10.6:1 and I would like to lower it to 10.25:1. Would it be OK to use a .060 head gasket? I won't know the exact numbers untill I measure the heads but I just want to know if it's OK to use a head gasket to change the c/r? Thanks

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ViennaHog

· #2 · Dec 31, 2005

csa98271 said:
Hello
Is it OK to use a thicker head gasket to lower the compression ratio in a TC engine? I have a kit that says with a 85cc combustion chamber and .040 head gasket the c/r will be 10.6:1 and I would like to lower it to 10.25:1. Would it be OK to use a .060 head gasket? I won't know the exact numbers untill I measure the heads but I just want to know if it's OK to use a head gasket to change the c/r? Thanks

The experts on the forum prefer a 0.030 gasket to maintain a squish between 0.020 and 0.040 which helps improve flame travel through the chamber. If you follow that logic you may have to discard your high comp pistons and replace them with a combination of flat tops and a thinner gasket like the Cometic MLS 0.030.
Look at http://v-twinforum.com/forums/showthread.php?t=66831 post 18 and have a look at the comp calulator. Welcome to the forum

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GRock

· #3 · Dec 31, 2005

It is absolutely OK too reduce your compression by adding a thicker gasket. As long as you have to remove the heads anyway, you can also have a shop remove a bit of material from the combustion chambers and / or add compression releases.

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