'99 YZ400F Smoking


2 replies to this topic
  • 1991CR250RBEAST

Posted October 06, 2011 - 01:08 PM

#1

I have great compression and don't have any power loss but I'm getting lots of smoke from the exhaust. If the rings are good then what else could it be? :smashpc:

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

Posted October 06, 2011 - 01:23 PM

#2

First, determine if it's smoke you see or steam. Steam will vanish into the air as it drifts away and cools off, smoke won't.

If it's steam, it's most likely a head gasket.

If it's smoke, and it smokes more under power than off the throttle, it's probably oil rings, which can be bad in spite of good compression rings. If it tends to smoke more when you first open the throttle after coasting down, but the smoke tends to stop if you leave the throttle open some, it's more likely valve guide seals.

  • 1991CR250RBEAST

Posted October 06, 2011 - 03:42 PM

#3

There is very little smoke while on the throttle but when it's idling it seems to smoke more. If it's been sitting for a day or so you would swear the world was on fire when I start it. My guess is oil seeping onto the Piston while sitting then when starting it burns up.I believe you hit the nail on the head.





Related Content

Forums
Photo

Should I buy this bike? help....... by Numsa Hul


Dirt Bike   General Dirt Bike Forums   What bike should I buy?
  • * * * * *
  • 10 replies
Forums
Photo

BIGBORE FOR YZ450F 2006? by Taattie94


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

Chubby dad, looking at bikes , First trip to the orange/black forum ! by Slow_ride


Dirt Bike   Make / Model Specific   KTM   250-530 EXC/MXC/SXC/XC-W/XCR-W (4-Strokes)
  • Hot  28 replies
Forums
Photo

05 yz450f not fast enough by RedeyeYZ


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

James Stewart back on a YZ450F by YamaLink


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  47 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.