Top End Rebuild. When to replace?


1 reply to this topic
  • mnm567

Posted April 20, 2005 - 08:01 AM

#1

I recently acquired my 05 450 in October. Switching from a two stroke, I am not sure when I should consider a top-end rebuild. I have a hour meter on the bike, so how many hours should I allow pass before the rebuild. I race about 7, 1 hour long GP's a year and ride aggressively any other time. Thanks, Matt

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

Posted April 20, 2005 - 08:48 AM

#2

It will vary from one bike to another based on a bunch of variables. There's no set time. My '03 still doesn't need it. I did replace the cam chain about two months ago, though.

I usually suggest that you go by what you find when you do a valve adjustment. Once the shim size in any valve goes past .20mm smaller than what was in it originally, it's time to replace them. The nitride hard coating on the valve face is worn through at that point, and the valve faces will start to wear rapidly, if they haven't already. Change out the valve springs, too.

Once you're in, you may as well at least inspect inspect the piston and put a new ring set in it. Replacing the piston is probably wise, even if it looks near perfect, but it may not be absolutely necessary.





Related Content

Forums
Photo

YZ450F 03 Sparks driving me crazy by SirAttard


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

Megabomb Fitment by 288yz450


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

Thinking about Yamaha 250... by Arctic Pride


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 replies
Forums
Photo

Snake pit oct 30th by The Anvil


Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 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.