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Hamish

Valves - just in time!

12 posts in this topic

Hi everyone, been a few months since I've been in here. Thought i'd share this little expereince with you all. I've known for a while that my centre inlet valve was pretty much buggered (on the smallest shim, clearance closes up 0.05 ever 10 hours or so). Little did I know just how close to disaster it really was. I'm feeling lucky so I might go buy a lottery ticket.

Inlet%20valve.JPG

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OK... everybody might laugh but I'm a valve newbie. What's wrong with this valve? (If it does not take too much of your time) :naughty:

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the hard coating has worn off this valve causing it to seriously wear on the area that touches the valve seat. The signs that you bike is suffereing from this problem is when your valve clearance keeps closing up. This is indicating that the valve is sinking deeper inside the head. It wouldnt be long before this valve 'mushroomed' because the area above the seating surface has worn that thin that it simply bent. Hope this makes sense. The bottom line is this. A broken $100 valve will cause $1000's of damage. It's cheaper the replace the valves first, than have to replace the piston, barrel, head and the valves.

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What Hamish said. :naughty:

I finally had to re shim my 99 WR 400. It was just under spec.

I had 3 175' a 174 and a 172. I am assuming they were stock although I bought the bike used in 2002. I put 170's in all but the middle valve where I was able to use the 172. How many more times do you think I will be able to re-shim

before replacing the valves? How far before the hard coating is gone?

Oh yeah Hamish, how do you like the Maxxis IT on the front? I just bought one haven't tried it out yet. I have heard mixed reviews about them. I think I should have bought the SI. They seem to have a very hard side wall and was thinking

about running about 11 pound PSI in them.

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is that what you were talking about? margin thickness?

433.jpg

could you bamster please check up in your book the thickness size for the 99WR since I dont have the original book :naughty:

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What Hamish said. :)

I finally had to re shim my 99 WR 400. It was just under spec.

I had 3 175' a 174 and a 172. I am assuming they were stock although I bought the bike used in 2002. I put 170's in all but the middle valve where I was able to use the 172. How many more times do you think I will be able to re-shim

before replacing the valves? How far before the hard coating is gone?

Oh yeah Hamish, how do you like the Maxxis IT on the front? I just bought one haven't tried it out yet. I have heard mixed reviews about them. I think I should have bought the SI. They seem to have a very hard side wall and was thinking

about running about 11 pound PSI in them.

If any of the valves move more than 0.1 you are in the danger zone. The valves may still be ok, but it's due for an inspection. Remember it's free to pull it apart to have a look.To give you an idea, my centre inlet (the valve in the pic) was down to a 125 shim (the smalleest yamaha sell)

The IT up front is great in medium/hard terrain, but in sand or med it refuses to go in a straight line, except when you want it to turn, then it'll go in a straight line. :D One ride a few months ago I forgot my pump, and I knew the front was down on pressure but went anyway. It washed out big time and I did some cartlidge damage to my right knee. When I got back to the trailer I checked the tyre - 7 psi :) - silly me.

I normally run about 10-12 psi, about 15 if I am riding on the street.

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Thread hi-jack

I switched from M12 fronts to an IT, and I swear I've never had headshake that bad before. It was running it at 13 psi on some nice loamy dirt.

Has anybody else noticed this problem? Or could it have just been the track that day etc?

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Thread hi-jack

I switched from M12 fronts to an IT, and I swear I've never had headshake that bad before. It was running it at 13 psi on some nice loamy dirt.

Has anybody else noticed this problem? Or could it have just been the track that day etc?

lol, I'm glad it's not just me. anything over about 50mph she gets abit snakey, makes it more fun, just need to be careful landing fast wheelies.

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