WR 400 Rebuild

5 replies to this topic
  • motodiver13

Posted September 02, 2009 - 10:41 AM


Hi All,

I need some advice. I just picked up a 98 WR 400 that was sunk in some water. The bike was cheap and I need a good project. So far I have removed the top end but the bottom end is bound up. I am going to split the case and dig deep. While I'm in there I want to do some mods. I can't seem to find difinitive answers about my '98 from other threads, so here goes.

1. Is it worth it to go with the 426 rod?

2. Does anyone know of a good source for rebuilt cranks?

3. What years can I swap parts from, ie: piston, cylinder, auto decomp. cams?

4. Any other suggestions of stuff to do?


  • flyer05

Posted September 03, 2009 - 11:36 AM


When I went to a 420cc on my 400 I used some Hotcams with the auto decomp., well worth it IMO. Starts sooo much easier.

  • motodiver13

Posted September 03, 2009 - 06:19 PM


Thanks Flyer, Still debating on the Hot Cam or OEM '03. Next question- what would be the best way to go about cleaning the silt of parts, crank, transmission, etc?

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  • Flooder305

Posted September 03, 2009 - 09:27 PM


You need access to a solvent bath, parts brush, and compressed air for drying... Don't forget your nitrile gloves... Everything needs to be torn apart and cleaned. Hope you got a factory service manual with it... If not pick one up off ebay, like this one (http://cgi.ebay.com/...lsQ5fLiterature):ride: That will save you some head scratching.

  • motodiver13

Posted September 04, 2009 - 08:17 AM


thanks,i have a clymer manual, is that sufficiant? will the solvent bath damage any of the bearings?

  • pablo83

Posted September 06, 2009 - 07:35 PM


thanks,i have a clymer manual, is that sufficiant? will the solvent bath damage any of the bearings?

You can probably rebuild the engine with just the clymer manual, but the shop manual will provide more tolerance and maintainance information than the Clymer.

A solvent bath will not damage bearings, but it may damage seals depending on what solvent you are using. I've used mineral spirits on some rubber parts without damaging them. Keroseen would probably be the best if you are going to clean plastic/rubber parts with it. My current shop is in my basement and I don't want fumes in the house so I use a soap based industrial cleaner which is safe on rubber, but this stuff doesn't clean as well as petrolium based products.


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