Yz450f 2005 Engine rebuild: Advice needed!

1 reply to this topic
  • LewisJayBirch

Posted July 21, 2014 - 04:03 AM


Hi guys I recently swapped a KX 125 for a Yz450f 2005 that had locked up at low RPM's in first gear (Or so the guy says) the guy thought it had probably dropped a valve but upon further inspection, all valves where fine and un damaged along with the piston and the cylinder wall, what we found was the crank had seized causing it to have no backwards or forwards movement but still allowing it to move up and down slightly within acceptable tolerances, what I am wanting to ask is whether or not I will have to replace the top end too aswell as the bottom, the cylinder and piston are in good shape and if I was going to replace the piston it would be another £100 and then id have to get the cylinder honed again. Is it worth getting a fresh top end to match a new crank and bottom end bearings?

Cheers - Lewis

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

Posted July 21, 2014 - 07:00 AM


The top end is reasonably cheap by comparison.  If the rob bearing seized, the piston was probably distorted, and should not be trusted.  I would, at the least, replace the piston and rings.  Honing the cylinder with a "spring-ball" or "brush" hone just quickly enough to restore the original finish is advisable, but you could spend a little time with some Scotch Brite if you want to cheap out on the job.  Results aren't as good but it works, sort of.

Related Content


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

Is the 2016 GYTR Yamaha YZ450F too fast? by Fryboy

Dirt Bike   Special Interest Forums   Pro Racing
  • * - - - -
  • Hot  241 replies
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

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  57 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.