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Paewraul

WR SM takin heat

4 posts in this topic

So I just bought some Gripsters to attend some track days at NHIS on my '01 WR-426, and I'm getting some "concerns" from a track day organizer.

He told me this: "Keep in mind our last yamaha dirt bike threw a rod and blew up his motor... dumping oil on the track. My belief is those motors are not meant for running wide open... very few trails you can just leave it pinned."

From what I've read here, a buch of guys have run the WR's at the track, and I run mine on the street all the time. They seem to be ideal for switching between the two (track and street). I got in to the WR because it seems to be the "everything" bike.

Is he upset that a former track day attendee fouled up a track day or should I be legitimately concerned?

I'm looking for some input before I put any more money into the bike for the SM switchover.

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Hi,

I use my bike in Supermoto races during the summer. Thing what you need understand is that Supermoto and Iceroadracing both are complitely different to the engine wear than motocross or enduro. Taking this you should change piston and con-rod in every 100hrs then most likely you'll be safe. How often Husaberg, Honda , Kawasaki , Suzuki or any other manufacturers recommend this operations I don't know. But can't be any more than 100hrs.

Timo Mc

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I ran my 99 WR400 on the freeway and the rod to crank bearing failed. I managed to pull in the clutch and keep the motor in one piece but it could have gotten ugly. I was told by Eric Gore that this was more common with the 400's and that the 426 has a larger rod end than the 400 or 450. He also said when replacing just the rod the crank needs to be pressed back together with correct alignment or you will kill the crank bearings. Since the cam timing chain (that had stretched) runs on a permanent sprocket on the crank he felt it was best to just get a whole new crank and rod combo ($300). Eric also told me that the titanium valves were not as long lasting as the stainless steel ones so if you do tear it down to replace the rod bearing you might want to do a valve job with some after market stainless steel valves.

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If it is any guide or indication the beating the top end takes in SM the recommendation for the NEW Aprillia SXV 450/550 V-twin (the SM version)is to change the top end every 60 Hours. So, the 100 quoted above sounds a good ballpark figure when you compare the RPMs, 9-10000 for a thumper? versus 11-12000 for the V twin? :ride:

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