Ive been chasing an oil leak on my bike and thought it was between the trans and engine cases. Cleaned it up real good and took it for a ride. Got the lights out and looked again and the oil was running down from the head gasket, just the rear one.

So I ordered a cometic complete head gasket kit but with .30 head gaskets instead of the .40 stock size. I'm trying to boost compression a little to feed my Tman 662-2 cams.

My question is, will I be able to ride with the increased compression on my old map until I get a new dyno tune?

 

I don't see why not. The compression bump is not huge and doesn't affect airflow like heads, intake, exhaust, etc.

 

You may want to check your clearances when going to a smaller gasket.

0.100" doesn't sound like much but it could be the difference between a running motor and a couple thousand in repairs.

 

^The difference is not .100", it is 0.010"....No need to check valve to piston clearance with a ten-thousandth less, unless you want to.

 

Thanks.

 

It's only 0.010" difference I'd say you would be fine

 

According to the big boyz calculator you should go up .2 in compression with a change from .040 gasket to a .030 gasket on a 120. 10:39 with a .040 to 10:59 with .030.

 

I just wanted to be sure so I could ride it to my dyno guy instead of putting it in the trailer.

Also replacing the valve spring with some AV&V 650 beehive springs while the heads are off.

sporacer, I believe you have the S&S roller rockers as well. Did you use the stock support bracket or install a billet style? I was going to have the crank, heads done and upgrade to the 124 kit but decided on getting a camper instead. That and my wife just delivered our second son last week, so I better leave the rest of the mods until next winter!

 

You could shave .015 off the heads with the .030 gasket and get the compression (10:8) up to match the cams more for not much cost. I did use the Harley rocker supports part number 17675-01b. They were much tighter end play compared to the stock units. Expect some additional noise with the roller rockers. You wont hear it with the borezilla.

 

Thanks for the heads up on the support bracket, Ive been running the S&S roller rockers since last summer with the stock bracket and figured while I have the heads off adding the springs and head gasket that I might want to address the support bracket.