Triumphrat

Colibri · 04-05-2008

Ok I got around to checking my valves today since I have no idea when the last time they where checked and my bike has 20k ish miles on it.
Here are the numbers I got

intake
7 = <.152

1,2,3,4,6,8 = .152-.203mm

5 = .203-254

Exhaust
5, 6 = .203-.254

1 & 8 = .254-.305

2,3,4,7 = .305-.356

I know the intake should be .15-.25 and the exhaust should be .20-.30. So on intake #7 would I take out a shim? And on exhaust 2,3,4,7 would I add a .05mm shim? Also what is the diameter of the shims and are there other brands I could use, like yamaha or something? I dont mind ordering them from online since its going to be rather cold the next week or so anyways. So if you know of a good site let me know!

Yak · 04-05-2008

You dont stack shims, so its not a case of adding or subtracting a shim. You would have to remove the cam and pull out the bucket and measure the current shim with a caliper or micrometer. Often the shim size will be stamped on it, but some says it best to measure to make sure its still within its own tolerances. Then replace that shim with the proper size in comparison to give you the new measurement you are looking for.

BikeBandit.com carries the shims. Im not sure if they are universal between bikes. You could always take out a shim and take it to a local Yamaha or Honda dealer..etc.. and compare them.

http://www.bikebandit.com/houseofmot...d-four/o/m6897

Its typical that valves tighten over time, as there is more stretch in the valve stem then any of the other components that could get compressed. The constant pounding of a hot valve closing tight on the head is what causes this over time. So kinda odd to me that you have a loose measurement.

pete2 · 04-06-2008

Could somebody tell the diameter of the shims? If I get to know that, I can tell you whether Honda, Yamaha etc shims fit

Colibri · 04-06-2008

Thanks for the info yak! I went out and bought a better set of feeler guages and rechecked all the valves. Here are the problem ones

Intake
# 7 = .10-.13

Exhaust
#7, 4, 3, 2 = .30-.33

So are you saying the #7 on the intake would be the loose one? Is it worse to have the clearences higher or lower then what they are suposed to be? Im just not sure what exectly happens if they numbers are one way or another, I just know if the valves dont close far enough you could have burnt valves.

Tomorrow after work im gonna take the camshafts out and ill take the micrometer to the shims and see what diameter they are.

Yak · 04-06-2008

I've never done valves on a streetbike, only my 4-stroke dirt bike (2006 Yz250). The principles are the same on all "shim under bucket" systems though.

The lower the clearance the "tighter" the valve. Tighter meaning it sits closer to the cam than designed, i.e... not within factory spec. Has nothing to do with how the valve seats in the head.

A loose valve means that there is more clearance than the factory spec. So it sits too far from the cam. Disadvantage of a loose valve is a valve that opens too late, not getting the full advantage of the designed lobe profile and a premature wear because now the cam hammers the bucket on every revolution instead of gradually lifting it and also a noisy valvetrain.

As far as whether its better to be on the tight or loose side of specs. In the interest of not having to adjust valves as often its better to be on the loose side of the spec because as I mentioned, valves typically tighten over time. However, being on the tight side of the spec should theorhetically create a smoother and quieter valve train. Problem is, if it gets tighter it goes out of spec right away and requires yet another adjustment. Its better to be right in the middle if you ask me. Also, note how small the spec range is. In reality, you wont notice a differnce either way.

Colibri · 04-07-2008

Ah thanks again yak for that! Makes alot more sense now.

Ok got the cam out and for #2 the shim says its a 252 so that should be a 2.525mm shim but the micro meter says its a 2.50mm is it normal for them to be off by .025mm?
And let me make sure I get this right before I pick up shims. Since #2 was between .30-.33 ill call its 0.32. To get it in the middle of the specs (.20-.30) I would take .32-.25 which is .07mm. So then just add that .07 onto that 2.5mm thick shim and get 2.57 so just round up and I would need a 2.575mm shim.

Also the diameter of the shim is 7.44mm.

Ok the closest I could find was 7.48mm
http://www.procycle.us/hotcams/valve_shims.htm
http://www.cyclebuy.com/shopping/hotcams/shimkits.htm
which is off by .04mm which might work just fine so i will probably go by the yamaha dealer tomorrow and pick one up and try. I much rather buy them for .60 cents a peice rather than 8 bucks.