How to know if a bike needs Re-jetting.....?

I'm just wondering how to know if a bike needs to be re-jetted.......? Any advice !

Thanks ! :)

Lean usually comes with backfiring, surging, and a tin-can kind of sound. My WR used to surge an d the idle was very erratic when it was new (lean)

Rich will foulplugs, the tailpipe will become black/sooty, response will not be crisp, acceleration will feel sort of lame. Will atart w/o choke.

There are other signs, do you notice the bike running a little strange? If so, detail you're riding area,temp,elevation, and all mods with things you've noticed, and we'll try to help


Give us your symptoms and it will be easier to tell you what to do. Also give settings and altitude if you can. Usually you can tell a lot by the color of your spark plug. It should be a nice tan or beige color. There are ways to tune it for low throttle, mid throttle, and wide open.

My bike was running a bit lean, causing my bike to pop on decell. I was able to correct it by adjusting my air screw and going from the stock 42 pilot to a 45. My head pipe also glowed red excessively before the jet change, but mainly in the colder weather which causes your bike to run a bit leaner than when it is hot outside (cold air is more dense). Mine was jetted just about right for 800' ele and about 108 degrees f lol.

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