Is my yz400 in need for a rebuild?


4 replies to this topic
  • bubbaisthebest

Posted January 18, 2009 - 02:22 PM

#1

I got a 1999 yz400f during the summertime, and up until about October, it has run great. Now it is fouling spark plugs, 4 in three months, and it's not starting in one or two kicks like it usually does. I'm thinking that it's time for a new top end. Any thoughts would be appriciated. Thanks

  • Smokeslider

Posted January 18, 2009 - 04:15 PM

#2

Have you checked the valve clearances yet?

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • LEMMON1

Posted January 18, 2009 - 05:42 PM

#3

sounds like u have a jettin issue if ur foulin plugs...it ran great durin the summer time where its noticeably warmer. and now its gettin pretty chilly out now..yammies can get very touchy bout how its jetted durin weather changes

  • DeeCee

Posted January 18, 2009 - 07:40 PM

#4

First up I would check the valve clearances and give the carburettor a thorough clean out.

Hard starting is often a sign of tight valve clearances. The plug fouling could be due to your mixture being off.

  • grayracer513

Posted January 18, 2009 - 08:09 PM

#5

It's very likely that the problem is jetting related due to the cold weather.





Related Content

Forums
Photo

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
Forums
Photo

James Stewart back on a YZ450F by YamaLink


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  47 replies
Wiki
WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info


Articles
  • 0 replies
Forums
Photo

Megabomb Fitment by 288yz450


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

05 yz450f not fast enough by RedeyeYZ


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  38 replies
 
x

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.