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Can't figure out which circuit is rich.

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When I rev up my bike from an idle it is has a dead spot at the very bottom end of the powerband than it snaps out of it and revs right back up and then when I reach moderate rpms and let off it back fires. I need help on what circuits I need to rejet on. I have a 170 main, 42 pilot, 1 1/4 out on air screw. My bike is an 2004 CRF450 with pipe and kibblewhite valves, no major mods done to the bike.

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I have a 03 with the same problem.

I have been all over with jets. I even shimmed my valves with no luck.

I am up to a 172 MJ and a 48 PJ also have FS out 2 - 2.5 turns and it still does it. It is also a bit hard to start when cold. Have to kick it about 10 times

to get it to fire then it dies and have to kick 2 more it fires then dies. after the 2rd attempt it finally fires and stays running but only with choke on till it gets warm.

Hopfully Eddie can help us out


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