turbowrenchhead Posted August 22, 2013 Report Share Posted August 22, 2013 My first rebuild I ended up with 130psi cranking compression w/ 20cc domes. The dyno set me up with 350 mains. This was with a cfm air box with foam filters. The cfm didn't pan out so well. I was getting a lot of water/dirt into the box and then running right into the carbs. I sold the cfm and went to a direct bolt K&N w/ prefilters. I blew the quad in WV on my last trip. I'm currently got the cylinders bored to 65.50 now and new cast pistons. The pistons must of have a higher dome on them because my compression is now at 160psi with 20cc domes. I have a set of 21cc domes on the way which should put me at 150psi. So my question is when you raise your compression does it require richer or leaner jetting. I have read that a raise in compression has more pull on the carbs therefore pulling more fuel. Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted August 22, 2013 Author Report Share Posted August 22, 2013 My squish is at .060 with the 20cc's. I'll redo a compression test and a squish test with the new domes when they come. Quote Link to comment Share on other sites More sharing options...
Zillaguy Posted August 22, 2013 Report Share Posted August 22, 2013 wow .060 is HUGE! You want your squish between .040 and .050 for pump fuel.. I like them right in middle at .045 with OEM base gaskets. Yes you'll need a jetting change... Higher compression creates more heat, and will need more fuel to cool down the combustion temps... Best to start with a 300 main and do a few plug chops, and fine tune the jetting based off your plug reading.. Don't just guess and cross your fingers... It will bite you in the ass in the long run, and motors are not cheap... 1 Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted August 22, 2013 Author Report Share Posted August 22, 2013 I am using an oem base gasket. I really don't want to go to a paper gasket. Quote Link to comment Share on other sites More sharing options...
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