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What is your jetting in the 600?
What is your initial timing?
Are you running vacuum advance? If so, how much?
What plugs (heat range) are you running?



I am not sure offhand on the jetting, but the plugs look good. I am going to throw a 750 on this weekend and see if it gets any better, will mess more with jetting then.

Initial advance right now is about 10-11 with 17 centrifugal. I had started with 17 initial.
Tried with and without vacuum advance, definately worse with vacuum advance, so it was plugged on most tests including 28 degrees total run.
I am running one or two steps colder than stock on the plugs, been awhile since I bought the plugs, hard to remember.

Non-quench, non-magnum heads.
Balancer is correct, verified during the build.

Thanks for the help guys, I really appreciate it, keep it coming!