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XR250rdr

Death of a 426

11 posts in this topic

So my friend has beat the crap out of his WR 426 over the past three years, including one trip riding from San Diego to Cabo (1300 miles or so). Now after (by his calculation) 230 hours of riding the bike gave up the ghost on a ride from Jawbone to Randsburg last weekend. Here are a few pics of the aftermath.

http://www.xr250rdr.com/Beene/Mvc-012f.jpg

http://www.xr250rdr.com/Beene/Mvc-013f.jpg

http://www.xr250rdr.com/Beene/Mvc-014f.jpg

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gotta keep an eye on those valve clearances.

My centre inlet is chewing up 0.1mm in <10hrs. (down to 120 pad)

New valves are on the way, so they tell me.

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I know he had the valves adjusted recently and he said they weren't on the move except for one had to be shimmed a tiny bit. Got an email from him tonight saying the cylinder was gone as well.

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Somehow i dont think that looks like a valve clearance issue

I would tend to agree with this as the cutout on the piston doesn't look like it got any slap from the valve until after it broke. Maintenance is key to longevity in any bike and fortunately I have never had a serious failure in any of my motorized vehicles because of that practice. No matter how much I have abused them. :cry:

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Somehow i dont think that looks like a valve clearance issue

That wasnt what I meant.

When the valve clearance is 'on the move' it is a sign that a valve may break soon. Rapid valve clearance changes are generally caused by:

a) when the hard coating on the Ti valve wears through. Many experts say that this coating thickness works as a good guage for the valves life.

:cry: a mushrooming valve

c) valve seat wear/movement, which to my knowledge is virtually unheard of in the 4XX range.

both of these scenarios are bad news and can lead to this type of failure.

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Well, looks ugly but cetainly fixable. One thing about 4 strokes, when they let lose, its spendy to fix compared to a 2 stinker!

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Did your friend repair the engine ? How much ? And what parts did he need for the repairs ?

Thanks

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That wasnt what I meant.

When the valve clearance is 'on the move' it is a sign that a valve may break soon.

I know from past foolish experiences with the old air cooled V.W.'s they had the same kind of problem with their exhaust valves... Due to the added heat they had a tendency to streach and after a while break. There was more to the service but back then I was a poor high school kid with no money. I mean whats cheaper four valves or a new motor. :cry:

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