Piston Change Question - What to buy?

5 replies to this topic
  • Dodger

Posted January 03, 2006 - 10:41 AM


Ok, so it's '06, and I have never had to shim my '01 WR426, nor have I replaced the piston in it. The bike still starts awsome, runs good, has good compression...........but, it's also 5 years old.

I think replaceing the piston about now should be in order. Do I just buy an OEM piston and rings? Should I be checking ring clearances before I buy a new set of rings? The fact that my bike still runs like an absolute champ makes me think that the cylinder condition must still be very good, so is there any reason to be thinking about oversized rings.........??? I can get the mechanical portion of actually replaceing the piston no problem, but just need to know what specs, and the propper steps on checking, buying, and installing a new piston entail.

Thanks for any info!

Dodger :applause:

  • Dodger

Posted January 03, 2006 - 02:02 PM


No one with any info??

  • byggd

Posted January 03, 2006 - 03:33 PM


It's always a good idea to have the cylinder checked while you have it apart so you don't have to do the job again soon and no one in here can tell you for sure if you need to go over sized. You might even think about having the valves ground while you are at it.

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  • 642MX

Posted January 03, 2006 - 04:55 PM


Chances are you don't need a piston yet. I did my 02 model last winter and everything looked brand new, it had alot of hours and seen alot of abuse too. If you must tear into it, I would suggest a Wiseco piston with 13.5:1 compression. It will add a noticable low end punch that pulls much harder in the mid range compared to stock. The downside is that its noisey, it actually has piston slap that you can hear.

  • rockieman

Posted January 03, 2006 - 05:26 PM


I am in the midst of rebuilding my '99 400.... one of my intake valves broke and ruined both the piston and the head. I went with the OEM 426 piston, cylinder and crank for my replacement. I don't think you have the luxuary to up the displacement and stick with OEM parts. I would consider some of the aftermarket big bore kits (Athena and MaxPower), from what I've read both seem reliable but perhaps a tad pricey. The reason I chimed in was to emphasize :applause: the drive train. Depending on the number of miles you have, I would encourage a new top end, valves, springs, and retainers.
Wished I would have addressed this (top end) before this past riding season.
My two cents!
Good luck!

  • byggd

Posted January 04, 2006 - 06:58 AM


Another thought. Do a compression test and "if it ain't broke, don't fix it" Just :applause:


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