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

2 replies to this topic
  • humbertob

Posted January 22, 2002 - 06:09 AM


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

Thanks ! :)

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • mcarp

Posted January 22, 2002 - 09:54 AM


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


  • MikeOK

Posted January 22, 2002 - 05:40 PM


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.

Related Content


yz400f throttle bog by yz400fmaniac

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • * * * * *
  • Hot  28 replies

Michigan Motocross Tires by 288yz450

Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply

2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

Need help by Goforaride

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  68 replies

YZ450F 03 Sparks driving me crazy by SirAttard

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.