Backfiring

I have a '99 YZ400 that sat up for a few months and now is hard to start and will only run with the choke on. :cry: With the choke off it backfires and will not stay running. The carburetor has been thoroughly gone through several times, the accelerator pump and pilot circuit are clean and working. Even with the choke on and running it backfires continuously. I preformed a cylinder leak down test and checked the valve clearance, both are with in spec. Please advise. Thanks in advance. :cry: & :cry:

I would have to say you have a restricted pilot jet. It doesn't take much to clog a pilot jet.

Did you remove the carb slide?

the pilot jet is clear and no i did not remove the slide.

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