'98 WR400 Rebuild options

23 replies to this topic
  • nnamssorxela

Posted April 08, 2012 - 06:34 AM


Thanks! I plan on checking up with the replating shop, the manual, a yamaha dealer, and of course the internet to see what the general consensus is for break-in, since I'm sure everyone has a different opinion on what is best (motoman, etc.).

I will be sure to update this thread as well as my others (it's been a problem for a while) once I get it all figured out.

Thanks again for your help.

Also, the piston pin had some visible wear lines and it stuck a little when coming out, so I hope that didn't wear the end of the rod at all. I will check for piston "rock" when I get the new piston and pin installed.

  • nnamssorxela

Posted April 13, 2012 - 02:00 PM


The parts came in today. The old and new piston are a little bit different in terms of valve reliefs. Will this cause any issues?
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  • RasmusDK

Posted April 14, 2012 - 12:38 PM


Dont know how close the piston goes to the valves, but those are there for a reason i guess :-/

  • nnamssorxela

Posted April 14, 2012 - 12:55 PM


I was mainly focusing on the area of the 3 intake valves. If you look at the old piston you can see that there are individually cut out, where as the new piston has all 3 intake valves sharing one edge. The center also appears to be the slightest bit higher on the new one. Hoping an expert can chime in here.


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