Need Advice on Valve Adjustment to Shim or not to Shim

I have checked my valves for the first time around 59hrs. My exaust valves are at the low end of the spec. @.20mm and ,23mm which is in spec.Tolerence of .20mm - .25mm.

But my intakes are .05mm and .08mm this is out of spec. The tolerence range is .10mm - .15mm.

I know the valve's and seats wear before the lifters and shims, so were always going to be chasing the ever shrinking tollerences.

I'm not as much concerened about the intakes being on the low end of the out of spec as I am about the exaust. I have always (on other engines) run my intakes tight with no problem.

I have talked to 2 moto/jet mechanics and they both said let it go and check it in 20hrs. Then if its changed, go ahead and adjust w/shims. They both have built several 250's and been very successful but never the 450.

Anyone got any advise..The enging runs great..

I'm no expert...but I would think that at lower RPM's, you should be alright, but at higher RPMs you'd be more likely to float your intake valves, and end up burning them over time.

As for the exhaust valves (either set of valves for that matter), the tighter they are (within spec) the better, IMHO.

I think your on the right track Beef, I'll go ahead tear it down and get the installed shim# and get it right. Now that you mentioned it I have felt the high revs fade a bit lately.

Thanks :cry:

On a new engine, the seat and valve angles are usually 1' different. Seats will be at 45,' while valve may be ground at 46' or visa versa. This makes for better sealing, drawback is as the 2 faces mate, the valve will sink down and clearances will decrease. I think this is why they want the first adjustment to be short. Once its done, the clearance will maintain much longer. But the valves can stretch also from higher rpm (racing) thus also reducing clearance. With less clearance, technically you'd get more lift/duration, but if the valve isnt fully seated when warm, you will be losing power. This is especially critical on exhaust. As each time the valve fully closes, it also allows heat to excape. If it doesnt fully seat, the valve face can overheat and melt down. AKA a burnt valve. Get it into specs. The engineers figured the specs to give you optimum HP. Besides, makes it easier starting too! Now if you all of a sudden end up with excess clearance, this is a sign of abnormal wear, ie cam, follower, valve stem tip etc.:cry:

Just double checking, most feeler gauges come in thousanths of an inch with metric measure underneath. Are you sure you read the gauge correct. I just checked my valves on my 2003 wr450 after 2 yrs of racing and they are fine.

:cry:

At which tempurature the valve clearance should be checked?

At which tempurature the valve clearance should be checked?
Always check valves when the engine is stone cold for consistancy, otherwise the margin of error may be too great. As things heat up, they expand and you'd be chasing different numbers depending on how warm your engine is, which is why valves are always checked when the engine is cold (consistancy).

Great thread, I checked my valves after 5 or 6 hours on the bike. The intake spec was right there but my exhaust valves are right at .20 and there's no way a bigger feeler would go in. The spec for the exhaust valves are from .20 to .25 but I could barely slide the .20 between the cam lobe and the top of the valve. Yes, the piston is TDC, I've checked and double checked with the bike being cold...

What do you guys think? How easy should a feeler gauge go in? :cry:

Thanks.........

Always check valves when the engine is stone cold for consistancy, otherwise the margin of error may be too great. As things heat up, they expand and you'd be chasing different numbers depending on how warm your engine is, which is why valves are always checked when the engine is cold (consistancy).

It's tough to check clearances here when the engine's cold, I prefer room temperature.:cry:

What do you guys think? How easy should a feeler gauge go in? :cry:

Thanks.........

I insert the guage and turn the engine a bit. If the cam pulls the feeler guage through it's too tight, if it doesn't I consider it OK. Sometimes it's tough to get the feeler guages in so I use that as my double check.

For folks who are super concerned about TDC, remember that you can rotate the engine quite a bit and still record the same clearance, as long as the lobes are pointing away from the bucket. If you wanted to do 1 cam at a time you don't really have to be near TDC, it just lets you check both cams at the same time without having to rotate the engine.

Dan,

Sounds like you are right at the tight end of the spec. There should be some drag on the feeler gauge - that way you know exactly where you are. I can't see how it would be possible to push a valve open with a .008" feeler gauge.

One problem I found when I opened up the valve clearances is that they become very noisy. The shims I had available resulted in 2 intake valves being on the loose end of the spec. If I were to do it again, I would have taken the shims to my buddy's machine shop and removed about .001 to .002" on the surface grinder. That way they start from the middle of spec.

I can't see how it would be possible to push a valve open with a .008" feeler gauge.
Be careful, its possible to do (I've done it). The feeler gauge is coming in at a low angle (like a wedge) and has a lot of mechanical advantage over the valve. The way I developed the "feel" is by starting with a gauge that is obviously too thin and then step up one size at a time until you feel a change in the resistance. It is very subtle, but very repeatable if you pay attention. What makes it difficult is the amount of bow you have to induce to the feeler gauge to get it in there in the first place - that accounts for a good portion of the drag you feel.

RNS, I just had the exact same experience on my bike. Intakes were just out of spec on the tight side and the exhaust appeared to be right at the min. tolerance. I did go from a 178, 179, 179 shim to a 170 for all 3 intakes. Now near the mid of tolerance. Maybe just my imagination, but it does seem to have a little more pop to it. Also a suggestion if you decide to shim, which I would recommend, wrap the frame tube above the head in saran wrap to keep debris from falling in. Go slow and take yoru time. The TT valve check instructions were my guding lista nd it worked just fine.

One question for those folks out there, would increasing the intake tolerance lean the engine out any?

You want to be careful with how hard you push on the feeler guage. Except for the real thin ones it is possible to move the valve a thousands of an inch or two if you overly force it in, giving you a false reading.

...

What do you guys think? How easy should a feeler gauge go in? :cry:

Thanks.........

Do it stone cold (excludes frostbite, as thats too cold) and the blade should push in without trying to bend etc. If the specs are .20 to .25mm (basically .0075 to about .0095) you should have the .2mm as the minumum, and .3mm should not go. Dont use standard feelerblades with the metric equivalent, get actual metric blades or go to http://www.worldwidemetric.com/metcal.htm and convert it. Problem with the SAE with metric, you will get the equivalent to the standard, not the specs the Yamaha manual shows for clearances and it can get confusing. If you replace a shim, roll the camshaft over several revolutions then recheck. This will settle everything in place and give you an accurate reading.

Toyota, thank you!!

Great thread, I checked my valves after 5 or 6 hours on the bike.

My dealer is telling me, don't sweat the valves until the manual spec., 1,800 miles (or a year); some here say 1,200 miles -- 6 hours? Is this normal?

Elton

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now