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  1. Need jetting advice - what size should I go?

    Yamaha ATVs
    So I have a 2008 Yamaha yfz450 with Yoshmira comp series full exhaust setup, and K&N air filter. It currently has a JDJetting 175 main jet in it but it’s running lean and backfiring everytime I let off throttle it backfires and occasionally even shooting flames. The K&N calls for a 210 main jet...