For Those That Haven't Inspected/Adjusted Your Valves

I highly recommend doing it, now. To check them is a no-brainer. To adjust them isn't hard, just a little time-consuming. I had 1 exhaust valve that was on the tight side and I let it go for a while because it was close to within spec. Well, to make a long story shorter I finally put it back in spec and WHOA, it was like I added a turbo charger to the thing.

Take the little bit of time it takes to check/adjust. You won't regret it.

I need to check mine. With the cold in town I suppose now is as good a time as any. Were you able to reuse the valve cover gasget?

Also could you read the thickness on the shim that you removed, or did you have to use a caliper to measure the thickness?


Rich, thanks for the advice. I have an 01' that I checked in August. It was ok then, but I'm going to look at it again this week.

I have a quick question however.

What are the symptoms of your valves being slightly out of whack?



Valves too tight will make your engine lose compression and lose the valve sealing seat. Valves too loose will rattle (tap, tap, tap..) and can eventually lose a little power too, due to less volume of intake and exhaust.

Rule of thumb: it's ALWAYS better to be on the too loose side than too tight.



If the shims were installed correctly, you should be able to read the printed thickness on the shim. They should be installed with the numbers facing up, or away from the valve stem. Mine were very easy to read (once I got the oil off).

Also, if you're careful you can reuse the cover gasket. I just did mine for the first time so I don't know how many uses, but at least once!


Yes, the numbers were very easy to read and I have reused the gasket twice already without a drop of oil oozing out of it.

Good description above about lose/tight valve conditons. I will add being a novice at thumpers it felt to me like I may have had a slight jetting problem when the thing just needed to exhale more.

Good luck!

I have had my valve cover off atleast 7 times and it still is in good shape, no leaks. It's time well spent to keep your bike healthy.


Well, my valve clearances finally went out of spec and my bike is apart in the garage right now. Taking the cams out was much easier than expected (much easier than taking apart XR's IMO) I will be getting new valve pads tomm. and will install them before the weekend! Later,


Garrett at your level of mechanical ability changing the valve shims could be done in your sleep.

p.s. which valves were out of spec and I'll assume they were on the tight side?

Both my exhaust valves are at .2mm

2 of the intakes are at .1 and 1 intake (far right one) is at .9mm I orded new shims today and they will be here next Tues or Wed! Here were my stock valve pads sizes:

Exhausts: 182 on both

Intakes: 190, 189 and 192

I took the cams out 3x today and they are real easy to get back in and the shims are easy to replace. The hardest part was getting the valve caps back on and making sure the "half moon" shaped circlip doesnt fall into the cases (which it did but I had a trusty magnet LOL)! Can you believe those valve pads cost $6.11 a piece??


Interesting, and no I can't believe they cost that much, with my discount I think I paid like 5.25 or something. I only had to buy one but in the near future I think I'll have to be buying more. Off the top of my head I think I had 200s, a 202, and a 189 from the factory. The mechanic at my local shop wanted to know if I just wanted to trade but since the 189 had to go instead of a round number I said no (and bought one from him instead).

On my -98 and -99 I used to grind down the shims,

Using wet sandpaper on a flat bed then a caliper to

measure the thickness.

That way I could keep the valves closer to tight than

if I had to buy the .05 incr. shims.

The titanium valves on the -01 seems to stay within specs for longer.

Well since the new valve pads dont come in until Tues or Wed next week (and I am riding tomorrow)...I went ahead and ground the stock pads down so that I would have the correct clearance! This method worked extremely well (I wish I hadnt spent $25 on the new pads)

I used a bench grinder, a 0-150mm micrometer, 600 grit wet sandpaper, and a piece of plate glass to grind them down! Now all the valves are right in the middle of spec, and they bike revs and runs ALOT better now (feels faster too)! Well I cant wait until tomorrow to ride it at Highlands! Later,


What exactly do you do to check the valves on theses machines, i have the manual but have never done this kind of work on a bike. any help would be appriciated, by the way i have a 98yz400

If any of you guys have the time, take the valves out of the head and lap them in with some fine grinding compound. wow it made my bike feel like a new bike better than the day i got it.


What did you do to your valve seats that made them require lapping to have a good sealing surface? Did your bike have lots of hours?

Originally posted by strack:

What exactly do you do to check the valves on theses machines, i have the manual but have never done this kind of work on a bike. any help would be appriciated, by the way i have a 98yz400

Strack - Go over to the WR side and click on the Technical portion. Go by those directions or use your manual. It's a simple job to inspect.

yeah i got it like 7 months ago and rode it like every other day to get practice on it and raced it in three classes sometimes every weekend till about a month ago. one night practiceing it started to backfire bad and since then had nothing but problems but i checked the valves about 2 months ago and found both exhaust valves were really tight. so being me i thought i would check the valves and seats for damage since i rode and raced it for so long. sure enough the 2 exhaust valves where not sealing, i havent really tested the bike yet cause of the weather here but no matter if its snowing saturday im goin to try her out.

How do you guys get a torque wrench on the valve cover bolts? My alen key sockets don't fit between the bolts and the frame.


sir- I think those allens are candidates for the "guess" torque method. I just finished putting my engine back together after a piston kit and there were 2 or 3 bolts that I couldn't get my torque wrench on, at least not directly. There isn't much space to work in there. Next time I think I'll have a in-lb wrench in 1/4 drive. The shop guys at work have one that goes to 200 in-lb and it's really small, would be great for those hard to reach bolts.

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