426 Engine rebuild advice

3 replies to this topic
  • q1445

Posted April 12, 2012 - 08:35 AM


I am the original owner of a 02 WR426. It has been an awesome bike! I probably have at the least 8000 miles on the original motor. Still runs great! I have always kept the valves in spec and done the other regular upkeep. It's loosing a little compression and recently the jetting has been off...........? I know it is getting tired and needs some love.

Can I just put in a new piston..... As long as the cylinder is clean or do I need to redo both the cylinder and the piston? Or can I just put in new rings?

Will the bottom end hold up to a new piston?

Who makes the best pistons? If the cylinder needs work, who should I send it to?

I know alot will depend on what I see when I open her up, but any advice before hand would be greatly appreciated.

  • bluesbiker

Posted April 12, 2012 - 08:54 AM


ive recently used a proxy piston when this seized my yamaha dealer supplied a piston and rings for more or less the same price,after my experiance this year genuine parts are a must gaskets etc,
ppl may argue but when it goes wrong its costly

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  • Just_a_trail_rider

Posted April 12, 2012 - 02:20 PM


I have another post going where I am freshening up my wr450 after about 8K + miles. I had only changed the piston once and it was a ProX, which is just fine. My cylinder, after all the miles and hard riding, still measures out at the OEM spec.

I would, however, take the head to a shop and have the recut the seats for the valves and put in new springs. That will cost you no more than $200. If you add a new piston to that little bit of head maintenance, it will be like new.

The bottom end will last forever. But be sure to check for play in the crank when you take it apart. Replace if necessary, but if you've don't your maintenance, it probably won't be.

  • q1445

Posted April 13, 2012 - 12:00 PM


Any suggestions on where to get quality head and cylinder work done?


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