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Discussion Starter #1
I've been working on getting my 2004 atp 500 running right. I'm almost there but still have a problem with the thing running lean.

It starts easily (when choked) but misses and backfires when revved up. Hard to get it to idle when warmed up with no choke.

I've gone over it several times and have not found an air leak.

I have replaced the carb with a NEW Polaris OEM Mukini BST. I assume that it was properly adjusted at the factory. Bad assumption?

I also replaced a scored exhaust rocker arm. Checked the cam and compression release. Both are ok.

However, I may not have it timed correctly. Had trouble finding tdc by looking in timing inspection hole.

So is it a carb issue or timing?

All ideas are appreciated.
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