Spark Plug YZ426

8 replies to this topic
  • 02YZ426

Posted May 29, 2005 - 11:32 AM


Can one of you guys that have a 426 that is jetted perfect please post a pic of your spark plug for me?? I am having a B**ch of a time getting my carb jetted and I would just like to compare my plug with another one that is running well. Thanks!!!!!

  • DoctorRzed

Posted May 29, 2005 - 02:38 PM


Plug should be brown. Light brown to lean black to rich. However if you run the bike long enough the plug will be black no matter what unless its to lean. The manuel explains this. Look for a jetting chart, I am sure someone has a link. Also find you altitude.

  • 02YZ426

Posted May 29, 2005 - 02:53 PM


This is what my plug looks like right now:

Posted Image

The one on the left is with at 162 main and the one on the right is with a 158main. Do these plugs look lean?? They both have about 1/2 hour of riding on them from new. Thanks

  • bigcheese

Posted May 29, 2005 - 03:01 PM


the pic of the two plugs are way to rich i would lean your bike out

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • 02YZ426

Posted May 29, 2005 - 03:04 PM


Way rich?? but they are white in the center. Wouldnt rich mean the plug should be black? I already leaned the main out 2 sizes! Wheres Grayracer when you need him? I bet he knows whats going on here!

  • sirthumpalot

Posted May 29, 2005 - 05:31 PM


Don't look at the plug, jet it by the way it runs. Plug readings can be useful but should not be used as the only (or most significant) tool for jetting the bike.

  • 02YZ426

Posted May 29, 2005 - 05:38 PM


Don't look at the plug, jet it by the way it runs. Plug readings can be useful but should not be used as the only (or most significant) tool for jetting the bike.

Ya, I here ya..... the bike is running good except it does have a slight stutter at steady 1/4 throttle, and Im not sure wether Im rich or lean, on main or pilot. Jetting 2smokers is much easier.

  • sirthumpalot

Posted May 30, 2005 - 10:57 AM


At 1/4 you're going to be mostly affected by the fuel screw, maybe a little by the needle and slide, but I'm thiking you can likely tune it with the fuel screw (or pilot jet) alone. Just go 1/4 turn on the fuel screw either rich (out) or lean (in) and see how it does. If the problem is still there then go 1/2 turn the other way. :)

  • zeroseven

Posted May 31, 2005 - 10:50 AM


Been here, been there, even tried that kit for sale on here. Gone back to stock and it goes better than ever.

Related Content

WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info

  • 0 replies

2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

Is it worth it? (Cam and High compression piston) by macgi77

Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies

Michigan Motocross Tires by 288yz450

Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply

First Hare scramble tips by dhend8

Dirt Bike   General Dirt Bike Forums   General Dirt Bike Discussion
  • Hot  33 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.