shim size questions

[snOhio]

went to check my valve lash today and came away somewhat puzzled.  as suggested, i picked up a 2.30 test shim.  i could not get my smallest feeler gauge (.04) under the exhaust cam on either side, so i swapped in the 2.30 shim and measured .53 on each side.  however, i pulled out 2.75 shims from each side.  the test shim would imply that those shims would give me 0.08 clearance, but that's not what i'm observing.

i'm leaning towards grabbing 2.70s and hoping for the best.  any thoughts?

[Slack]

Get a set of calipers and measure the test shim and the two 2.75's.  Just because they say they are a certain size doesn't make it so.  Then you'll know exactly which shims you need to buy.

[Kerry]

As you use thicker feeler blades, it becomes easier to "force" them under the cam lobe.  Sometimes, what you're really doing is pushing the cam follower (bucket) away from the cam lobe by compressing the spring a little.

I bet you'll be fine with 2.70 shims.  Meanwhile, you might want to go with a thicker test shim ... one that's closer to your current shim thicknesses.  Say, something in the 2.50-to-2.60 range?  (Sorry - you probably got the 2.30 size from an old recommendation of mine.)

[snOhio]

  (Sorry - you probably got the 2.30 size from an old recommendation of mine.)

don't put it all on yourself, but yeah, that's the size typically mentioned for a test shim that i found around here.  (side note: someone mentioned using a smaller diameter shim.  i discovered that a 25mm shim will vacuum itself to the bucket with the oil in the top end, and you won't be able to use the notch in the bucket to pry up the shim.  the you get to add an extra 30 minutes to the job.)

anyhow, i got some calipers and measured all the shims.  both exhaust shims measured around 2.70, and my "2.30" reference shim measured 2.25.  yes, it was zeroed, and for giggles i measured my feeler gauges and .04-.88 was spot on.

based on this, i'm not sure what i should do next.  grab some 2.60's and see what happens? i'd like to aim for .13ish of lash to be real safe.

[Kerry]

grab some 2.60's and see what happens?

That sounds good to me.  On the one hand, you might be able to use the 2.60's as-is.  But even if things don't work out that perfectly, you can at least measure the clearances more reliably.

Besides, from what I've seen with exhaust valves ... if you don't need the 2.60's yet, you probably will (at some point in the future) if you rack up enough miles.

[gsJack]

grab some 2.60's and see what happens?

That sounds good to me.  On the one hand, you might be able to use the 2.60's as-is.  But even if things don't work out that perfectly, you can at least measure the clearances more reliably.

Besides, from what I've seen with exhaust valves ... if you don't need the 2.60's yet, you probably will (at some point in the future) if you rack up enough miles.

+1

Once I got my tighter exhaust valve stabilized at the new wider .003-.005" (.08-.13mm) setting on my 02 it went another 40k miles before another shim change that it may not have even needed.  Now at 98.2k miles it will go over the 100k mile mark this summer.  The tighter exhaust valve on my 97 GS that ran at minimum factory clearances all the way was down to a min 215 shim before the 80k mark.  Doubt I'll ever even check valves again, it's become a contest which one of us will live the longest, me or the 02 GS.   

http://www.gs500.net/gallery/data/500/GSvalvelogs.jpg

[snOhio]

i thought that it would be a good idea to pop the 2.60 out of my intake valve to check the exhausts.  naturally, i realized this 5 minutes after i put everything back together.