Valve Clearance

Well, I finally got around to pulling the valve cover, and checked my valves. I had hoped that since the bike seemed to have regular maintenance and the carbs were mostly clean, maybe the valves would be passable. However, after reading all the tales of woe with improperly adjusted valves, I decided to suck it up and find out first hand.

Turns out its a good thing I checked them, only one intake valve had any clearance, although all exhaust valves were within tolerance. After seeing the shims, I wonder if the only good intake valve was replaced at some point, since the numbering scheme does not match the rest. Below is a quick break-down of what measurements I got from cylinders 1-4, left to right.

Intake
0.005" 0 0 0
Exhaust
0.006" 0.006" 0.007" 0.006"

Intake Shims
285A Y285 Y285 Y290
Exhaust Shim
Y275 Y265 Y275 Y270

My question now is, how do I swap the smallest shim out to check the rest? Can I simply remove the shim and proceed to swap it around, or do I need a shim in place before removing the shim tool? Also, since all the exhaust valves are on the tight end, should I go ahead and go down a shim size or just keep an eye on the clearances?

Speaking of the shim tool, I was not comfortable with sticking things in the combustion chamber, so I purchased a shim tool from our wonderful parts guru, Chacal. I must say it made the job have a little less guess work, and gave me a little more peace-of-mind. I took me 2 or 3 tries to seat it properly on the first go, but after that everything was smooth sailing!

I can post pics if anyone is curious, but I think bigfitz covered everything in his tutorial.

I look forward to your suggestions!

 

Looks to me that you need to keep #1 shim in place #2 & #3 = 275 and #4 = 280. I would leave all your exhaust shims the same. While the exhaust clearances are at the low end of the spectrum, they are still within the safe clearance range posted by yamaha. Intake valves more commonly tighten faster than exhaust valvesdueto the amount of dirt that may get through or past the air cleaner. The valves clearance tightens as components wear so you will want to check them occasionally to make sure they are within spec.

If you follow the equation below and compare to yamahas shim chart that is in the manual (or in the FAQ) yamaha specifies for the clearances to be set on the tight side.


A = (B-C) + D

A: new shim thickness
B: measured clearance
C: specified clearance
D: current shim thickness (285 = 2.85mm)

 

Keep one thing in mind: The clearance "range" is 0.5mm (.11-.15 or .16-.20) and the shims come in .5mm sizes. Therefore, there is only ONE shim size that will put you in spec on any cylinder. If "on the tight side" means DEAD ON the "tight" spec, I would drop down a size so you have some service life leeway.

Yes, you need to have a shim in place. Don't operate a valve with the cam directly on the bucket, I don't think it'll push down far enough to allow you to properly engage the tool. I'd send you some used shims but I already loaned mine to another member for the same reason. If I were you I'd "borrow" the 275 from the loosest exhaust valve and put one of the 285's in its place (for now) so you could use the 275 to check the "0" valves.

earz is probably right on his size guess or damn close.

Once you've got them all in place, turn the motor over a few times to be sure they're 100% seated and then check again (and record.)

EDIT Looks like I do have a couple used 260s left, PM me with your address and I'll mail them to you, send 'em back when you're done.

 

Thanks for the quick responses guys! Since bigfitz has been generous enough to let me borrow a shim, I think I'll hold off until I am sure what sizes I shoud order. It will be interesting to see how close your estimates are, earz!

I wish I had a compression test before tearing everything down, but I guess I will have to live with having an "after" test only.