400 spark plug question

3 replies to this topic
  • bubbaisthebest

Posted January 24, 2009 - 12:55 PM


I have fouled many plugs (cr9e) in my bike over the past few months. Would running a hotter spark plug (cr8e) get rid of the fouling? My last resort is to change the jetting. Thanks for any info.

  • Michael Cahill

Posted January 24, 2009 - 06:36 PM


I had this same problem in my bike.
I ride alot of trails, so i figured since im not really ever getting into the top end much, the engine never really gets a chance to burn nice and hot to keep the plug from fouling.

so i leaned out the needle jet by moving the lil circlip up one position.
this seemed to have fixed the problem, because i have yet to foul a plug, and when i pull it out to check it, its always nice and tan looking :banana:

so basicly,
plug fouling= over-rich condition.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • grayracer513

Posted January 24, 2009 - 10:04 PM


You are running too cold a plug. The bike calls for a CR8E.

  • bubbaisthebest

Posted January 25, 2009 - 06:27 AM


Thanks for the replies, you answered my question

Related Content


James Stewart back on a YZ450F by YamaLink

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  47 replies

Yamaha YZ450F 2017 by Chris.GVS

Yamaha YZ450F 2017
  • * * * * *
  • 1 review
  • Last review by Tommyk_55
  • On January 15, 2017
WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info

  • 0 replies

Megabomb Fitment by 288yz450

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply

BIGBORE FOR YZ450F 2006? by Taattie94

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.