No valve clearance?

[Furious D]

Well , I decided I would check the valve clearances on my 80 GS-850. I was hoping to complete it and have it road-ready for next week but I ran into a problem.


I had some popping back thru the 1,2 exhaust so I decided to check them first. There is no measurable clearance on the #1 exhaust. The smallest feeler guage I have is .02mm and I cant get it to go in. Even on the intake it is tight. The intake has 2.75mm shim and the exhaust is 2.65. I tried swapping the thinner one to the exhaust and still it wont go.


I am thinking the only thing I can do is go buy the thinnest shim available, install it and get the reading from there ? I'm using the tie-wrap method to remove the shims. I dont have the tool so rotating the cam without the shim in place is out of the question.


Any ideas?

[bwringer]

I've never seen a .02mm feeler -- are you sure you're not using an inch feeler? (.002")

Anyway, if that's not the problem, it is common to need to go down three or four shim sizes when you have a zero clearance situation.

I'd get a 2.55 shim and maybe a 2.50 shim and go from there.

Where are you -- is there a GS-er around with a shim collection?

[Furious D]

Yep , Its a .002 mm. The local dealer wont be open till Tuesday so I might see if I can have some machine shim-stock tommorow cut down to a 29.50 mm circle at work. I know it comes in 2.50 and 2.25 mm .

[DanTheMan]

Yep , Its a .002 mm. The local dealer wont be open till Tuesday so I might see if I can have some machine shim-stock tommorow cut down to a 29.50 mm circle at work. I know it comes in 2.50 and 2.25 mm .

That sounds like an idea. Otherwise, JoeNardy probably has some extra shims lying around....

[tkent02]

Here's a trick to see how thin you need the shim to be. Try to spin the shim in the bucket with your finger with the cam in the correct position. If it spins, there is at least some clearance, one size smaller should put you in the right range. For instance if it's .01mm clearance, .05 smaller would be .06, within limits. If you can't spin it there is zero or less clearance, two sizes smaller should put it in the range (.1mm maximum). It may take more than two sizes smaller, but if so the valve are likely to be burnt anyway.

You still have to check once the shims are changed, but it's just an easy way to help you guess correctly.

[Furious D]

I went out and put the shims back in their original locations. I can spin both with my finger so there must be a little clearance , .01 mm or Less?


I might see if the guys in the machine shop can shave a few thousandths off them. I know we have the equipment to grind it but I'm not sure we have a jig to hold something that thin.


I hope the other 6 valves go a little smoother, This might take some time.


Thanks for all your help

[mike_of_bbg]

I'd catalog all the sizes you have and need first then see if there are any swaps which would work. You're bound to have a variety of sizes and may only need to buy 2 or 3 shims. Do you have a metric micrometer or digital calipers? Invariably two or three of the shims won't have markings

[1948man]

Yep , Its a .002 mm. The local dealer wont be open till Tuesday so I might see if I can have some machine shim-stock tommorow cut down to a 29.50 mm circle at work. I know it comes in 2.50 and 2.25 mm .

You're still saying .002 mm. Do you mean .02 mm? If it's .002 inches that would be about .05 mm

[Furious D]

You're still saying .002 mm. Do you mean .02 mm? If it's .002 inches that would be about .05 mm

Now I see, Yep its .02mm. This particular feeler guage is metric only and goes down to .02 . My other ones are standard and metric and .04 is the smallest. Maybe I need some new glasses

[Allie]

Oy, I was just through all of this in the fall, what an extravaganza. I still owe pies to several GSers. Tkent gets one for that shim spinning tip too!

[tkent02]

Pumpkin ?

[Allie]

Pumpkin ?

Humble!