YZ / WR Valve Adjustment,,,, Needed?

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#1
Ok I got my bike used with about 600 miles showing on the Odmer. So I start going over it after 3 rides and find some pretty shocking stuff. Well, while its apart and clean, Ill check the valves. I start taking the motor mount bolts off and the last one, the allen head strips out :think . So I figure Ill drill it out and keep going. But Im all upset and its getting late and I want to ride the next day, so I say forget it and put it all back together. My question is, Have any of you boys (or girls) that beat the snot out of these bikes had to acutally adjust the valves on em? If so how oftern? And why would you have to remove the radiators to do it like the book says?
 

J.B.426

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#2
You do not have to remove the radiators to check or adjust the valves on these. Follow the manual otherwise. I have checked mine twice in the last year and they are still within spec. They are very easy to check, it shouldn't take you more than 20-30 minutes. I imagine if you're putting many hard race hours on the engine more adjustments may be in order, although I've heard of many race bikes that have not needed valve adjustments for a long time. I'm sure some more people will offer their experiences.
They tend to tighten as they wear.
 

holeshot

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#3
valve adjustment

The clearances on my '00 426 intakes were tight from new, but since I've adjusted them, the measurement has held steady.

I replaced those dang allen head bolts with hex head bolts of the same length. After a time, I removed the tank to check if the hex heads had interfered with the underside of the tank, but no problems. I guess Yamaha just wanted to torture us. :think
 
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#4
I've seen a number of engines that went two full seasons without changing a shim. The valves, seats, and followers hold up well and clearances don't move much.
 
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#5
Rich is bang-on, I'm on season 3 & haven't had to adjust yet (but I've checked them 3 times). The old 'better safe than sorry' principle definitely applies here.

It doesn't take long to check , and you will sleep better knowing they're in tolerances.
 
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#6
Good deal! I have not read about anyone having to shimm them so I did not think I would have to. I will check them, but not for a while untill I have to go digging under there again. (I only use a scrub brush, puddy knife and a towel to clean my bike most of the time) Thanks for the bolt info, I was wondering if I could replace em with regular bolts. My only thought besides clearance was that Yamaha was trying to shave a few grams off the weight. Sounds silly but I was looking at a feature in Dirt Bike on Travis Pastrata's Works ride and saw all sorts of stuff like the center of all the hex bolts was drilled out and all flat washers looked aluminum and had like 1/16 holes drilled around them. But the WR bolts are rounded so I cant even get a vise grip on it :think Grrrrrrr, Ill be replacing em with hex heads too!
 

NVR FNSH

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#7
Actually, I did adjust the valves on my '99. 4 of 5 were a .001 below the range so I adjusted them back to nominal. One suggestion - try to find a 'narrow' feeler gauge.

Brian