Shimming Reseated Valves

[Guest]

This problem has probably already been covered on another thread, but a search doesn't quite give me an answer.

I had the head of my '80 GS850 redone at a local head specialist.....new seals, new exhaust guides, a bit of intake porting, and lap the valves.

After re-installation on the motor, I am trying to re-establish the right valve shim set for it. Obviously, my old shim combination was too tight (after valve lapping), so I hunted down thinner shims, and tried them. Most are in the right range (2.20 to 2.30), but three intakes are right down to 2.15mm, and a bit tight at that (0.03mm clearance).

My questions are thus: what do I do as these ones with the thinnest shims wear, and tighten up even more? Suzuki only lists to 2.15mm, and that's all I can find in the local shim collections. Do aftermarket shim makers go thinner? Should I actually take the head back to the head shop and get the valve stems trimmed to get back into the middle of the Suzuki shim range? (sniff, sniff, another $200 for a Suzuki head gasket..)

[hampshirehog]

You can't use thinner shims - there aren't any available (plus the cam lobes would probably start hitting the buckets). The usual thing is to take a smidge off the valve stems (= head off, etc). However, there was guy on here who was going to try and grind down the inside of a valve bucket and this looked to me as if it should work. I don't think he ever came back and gave the results but you might have better luck using search.

[Big T]

The Shim Club will grind you whatever size you want

But, it sounds as if the machinist cut pretty deep seats in your head. Maybe he;ll drill your buckets to compensate

[Nessism]

I'd pull the head back off, remove the valves, and have them faced to reduce the stem length. The valves will continue to sink into the head so you need room for future shim reductions. No way I'd mess around with grinding the buckets at this point in the rebuild process. The engine is fresh so fix it the right way.

[tkent02]

I wouldn't see a problem with grinding a little bit off the tit on the underside of the buckets. Buckets are cheap, who cares? Pulling the head again is silly.

[Nessism]

I wouldn't see a problem with grinding a little bit off the tit on the underside of the buckets. Buckets are cheap, who cares? Pulling the head again is silly.

How can you assure those little nubs under the bucket are square if you grind them, and what would you grind them with anyway? And how much do you think you can cut them down? My guess is you will only get a few thousands off them anyway. It might get you on the road but for how long before you once again run out of options?

I've skimmed the back side of valves before using a disc sander. I set up a V-block at 90 degrees to the disc and fed the valve in by hand. Measured the overall length of the valve and made sure to cut them all the same. The valve shims on that particular head were all under 2.15 and when I was done they took 2.5 - 2.6 size shims. Much better.

[Runningdog]

The Shim Club can apparently supply down to 1.9mm, with no bucket interference....a temporary fix, but it will get me a few more years out of the engine the way it is before I need to dismantle again.

The only issue that stuck in my throat about tearing it down now was the cost of those darn gaskets....I haven't even had a chance to run the engine.

Thanks, all, for the very good replies....I know now what I have to do/should have done.....

[SqDancerLynn1]

That sucks, but the clearances should have been checked before the head was installed

[Runningdog]

Naturally, you're right, SQLynn...I'm learning an awful lot on this re and re....will know all kinds of things for the next one.

[Nessism]

I just measured two different buckets and the lip on the top measures 2.09 mm. This basically means you can not use a shim thinner than 2.10 mm in there or the cam will hit the edges of the bucket. Personally, I wouldn't use anything thinner than 2.15 like Suzuki intended.

[waterman]

I agree with Mr Ness, pull head and have valve shortened. I wouldn't think it would be that costly to have them fixed.

If you haven't run motor, I would tear it down and reuse head gasket, the rest should be okay unless you have cemented them in place with some gasket sealer. Maybe I am off kilter on this but I had pulled the head on my 650 when I realized that I had forgot the corner orings on head. It hasn't given me any trouble yet from head gasket.

[Runningdog]

Oh, sure, getting the valves ground down would be really cheap...the head shop is really good that way, likely free.

I'm going for 2.10 shims, which is pretty much the limit, as I'm learning....

As for re-using the head gasket, even though the engine hasn't run, It has been torqued down for a couple of months (I know, I know, how could I let this project sit so long.....working 6 days a week since Easter, family stuff on Sundays), so I suspect that the head gasket is stuck in one thickness by now.

I do have an Athena head gasket sitting on my desk, but have heard conflicting things about non-OEM head gaskets. I'll likely run the bike for the summer, then do things right next winter (assuming everything works out as I hope).....ever hopeful, ever naiive

[Guy]

Suzuki have good reason to specify 2.15 as the thinnest shim available because of possible lobe/bucket edge interference. How did they end up so out of spec? Were the valves just lapped or were the seats re-cut?
Sounds like the shop have pocketed the valves on you. Go back and take it out of their hides.......
Remove the head and grind 0.5mm off the stems.

[Runningdog]

"That sucks, but the clearances should have been checked before the head was installed "

OK, I've decided to go the right route, and get the valve stems shortened. Really, now, a head gasket is only a few hours work to pay for....

Now, my next question is, "how do you check the valve clearances before mounting head?" Obviously, it's no problem putting just the head back together on the bench, but then how do you turn the cams to check clearances at each cam lobe? Will they move by turning each cam by hand? Can I develop enough torque just with the little pinkies to depress each valve? A puzzler.....

[TPL]

Turn the cams by way of the gears (good pair of gloves), should be able to do that. Shortening the stems is the best route instead of shaving the shims so close to the bucket, you won't have to pull the head of again in 5k miles.