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seamus1618

wr400f rebuild?

9 posts in this topic

Okay, my 2000 wr400f was flooded with 4' of salt water during Hurricane Ike. I've probably put about 350 miles of trails on the motor since then without any problems but I feel that the life of the motor was severely shortened by the salt water. Normally I wouldn't worry too much about when the motor blows but I'm planning to make a trip to Colorado this summer and I don't want to have a motor hand grenade while I'm on my vacation.

I would like to up the engine size just because. I'll be doing the motor work myself so I'm looking for a complete kit. Anybody have any suggestions on a quality, complete big bore kit and where you could find it?

Also I would like to install the auto-decompression cams while I'm at it. Anybody know where I could find stage 1 auto-decompression cams?

Should there be anything else I should do while I have the motor down considering the conditions the motor was exposed to?

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Well for the auto decompression i would order the hot cams kit you can git from dennis kirk or rocky moutain For the big bore kit i couldn't find one but i think you could take it to a machine shop and git it bored out or you could go to max power and they make a bolt on kit for a yz400 which i think would work but im not sure u would have to do some more research.

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Looke here http://www.powroll.com/P_YAMAHA_YZFWR426F.htm. If you have already put 350 miles since being submereged you're probably ok. The WR uses dry sump for both engine and trans oil, which I assume you have changed a couple of times by now, you hsould have flushed out any residual salt water.

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Looke here http://www.powroll.com/P_YAMAHA_YZFWR426F.htm. If you have already put 350 miles since being submereged you're probably ok. The WR uses dry sump for both engine and trans oil, which I assume you have changed a couple of times by now, you hsould have flushed out any residual salt water.

Anybody have any experience with stroking this motor?

Sounds good, but I would like to hear some first hand feedback.

Some of the big bore kits I've found so far:

http://kustom-kraft.com/YAMAHAKITS.html

http://mxpartsonline.com/Merchant5/merchant.mvc?Screen=PROD&Store_Code=mxparts&Product_Code=BBYZ420F&Category_Code=BBKITY

http://www.thumperstore.com/YZF400_TO_430_BIG_BORE_KIT_p/yzf400%20to%20430%20kit.htm

http://www.lukesracing.com/luksr/yz400f.htm

Opinions?

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426 rod if you're going to go with Luke's 444 kit. 400 rod will work with their 420 kit. If you are going to do the crank anyway, go with 426 parts. Te small end bearing is bigger. One thing to consider on the crank, if you are going to rebuild it, it's pretty much a push for parts and labor vs. a new 426 crank from the TT store. If I remember right, the 400 cranks are quite a bit more pricey than the 426ers. You will need to get a new balance shaft gear and new primary gear as the 426 crank is splined, not keyed...other than that, it's a drop in.

The 444 kit with 13.5:1 piston and hot cams is really a great combination. In addition, I have a YZF pipe (with Pro Moto Billet end cap/spark arrestor) and a JD Jet kit, PowerNow and Boyeson QuickShot. Whe I put the bike back together, I had to go up one tooth on the front sprocket to make first gear even a little usable!

You may also want to think about going to the 426 clutch...it's a bit more durable as well.

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426 rod if you're going to go with Luke's 444 kit. 400 rod will work with their 420 kit. If you are going to do the crank anyway, go with 426 parts. Te small end bearing is bigger. One thing to consider on the crank, if you are going to rebuild it, it's pretty much a push for parts and labor vs. a new 426 crank from the TT store. If I remember right, the 400 cranks are quite a bit more pricey than the 426ers. You will need to get a new balance shaft gear and new primary gear as the 426 crank is splined, not keyed...other than that, it's a drop in.

The 444 kit with 13.5:1 piston and hot cams is really a great combination. In addition, I have a YZF pipe (with Pro Moto Billet end cap/spark arrestor) and a JD Jet kit, PowerNow and Boyeson QuickShot. Whe I put the bike back together, I had to go up one tooth on the front sprocket to make first gear even a little usable!

You may also want to think about going to the 426 clutch...it's a bit more durable as well.

I didn't see the 444 option on Luke's website, is it no longer available or do you have to call and ask?

Also I am assuming the YZ400F big bore kit works in the WR as well?

I am going to try and stay away from splitting the cases so it sounds like 420 is as big as I can go.

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I think I'm going to get the 420 kit from Luke's Racing with the 12.5:1 compression piston, hopefully the lower compression will mean longer engine life since I only ride trails.

Any suggestions on which cam from hot cams would be a good match for this setup?

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