Help with my 2000 YZ426F

3 replies to this topic
  • Strawbs86

Posted May 16, 2016 - 01:54 PM


Hello! Any help would be great on this. I bought a 2000 yz426f that was completely dismantled after a valve strike on piston. Head was rebuilt by previous owner. Replaced cylinder and piston using instructions ive found online with genuine manual and it ran fine for about 2 hours. New gaskets and torqued to spec. Clutch started slipping while riding then found leak from head gasket and lower gasket was wet. Stopped bike and let it cool. No overflow from top of rad so didn't think it was over heating. Noticed oil was thinner so presumed coolant had got into oil. On dismantling I noticed head bolts were a tad loose. New piston was completely scored down one side and rings were almost welded in on one side. Cylinder scored, looks knackered.

Looks like I've bought a money pit :( what do you guys/gals recommend?

I sent head off today for a skim. Should I do pressure test too? New piston and cylinder.

Worried about wasting a load of cash on this. Any ideas? Am I best sending off to a pro to do?!

  • Wild Alaskan

Posted May 16, 2016 - 02:19 PM


did you put oil in it? they have a frame oil tank

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Strawbs86

Posted May 16, 2016 - 02:49 PM


Yea I put oil in 1.7ltrs I think in total. There was oil running to head and I cleaned oil filter too

  • Wild Alaskan

Posted May 16, 2016 - 04:57 PM


hard to say, its possible that the crank or cases are damaged causing the piston to not be riding square to the bore,

Related Content


Yamaha YZ450F 2017 by Chris.GVS

Yamaha YZ450F 2017
  • * * * * *
  • 1 review
  • Last review by Tommyk_55
  • On January 15, 2017

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

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

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

05 yz450f not fast enough by RedeyeYZ

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

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 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.