shim bucket problem

[fallous]

So I was doing a valve shim clearance check on ye olde GS850 and ran into a bit of a problem. The exhaust valve on the #2 cylinder opens and closes fine from what I can see while looking into the spark plug hole while turning the crank, and using the zip tie tool lets me know it's at least opening and closing enough for that to work to relieve tension on the cam when I'm checking clearances.

The problem is the bucket refuses to rotate, although it moves freely up and down. I mean, it's STUCK despite some rather manly attempts to move it with a flathead screwdriver. Luckily I can just barely get to the notch to pop out the shim so swapping that won't be an issue. What I am concerned about is why this shim bucket is acting in this manner.

I'd really rather not be tearing deep into this motor right now.

 

[Nessism]

The exhaust side shim buckets tend to get cooked; I've seem quite a few of them that are black and blue from heat, along with a good deal of scuffing on the side. My guess is that this is what has happened to that bucket. If you feel motivated, pull the exhaust cam and then the buckets - check them all and figure out what's going on. This is doubly likely to happen if the bike is running lean due to inappropriately jetted carbs and/or leaky carbs. Best to take care of things like that and don't let them fester.

 

[Don-lo]

The bucket will also be hard to turn if the shim is too big and putting pressure on the valve. Did you get any clearance when you checked that valve? Do you have good compression in that cylinder? If the answer to both questions is "no", then go at least 4 sizes smaller on shims.

 

[Nessism]

The bucket will also be hard to turn if the shim is too big and putting pressure on the valve. Did you get any clearance when you checked that valve? Do you have good compression in that cylinder? If the answer to both questions is "no", then go at least 4 sizes smaller on shims.

I agree with Don, assuming you don't have a tie wrap inserted. My advice assumes you have the tie wrap holding the valve open.

 

[Don-lo]

Good point Nessism. I was assuming he was trying to position the notch before lowering the valve. Since I use the shim tool, that is the only time you can rotate the bucket.

 

[fallous]

The exhaust side shim buckets tend to get cooked; I've seem quite a few of them that are black and blue from heat, along with a good deal of scuffing on the side. My guess is that this is what has happened to that bucket. If you feel motivated, pull the exhaust cam and then the buckets - check them all and figure out what's going on. This is doubly likely to happen if the bike is running lean due to inappropriately jetted carbs and/or leaky carbs. Best to take care of things like that and don't let them fester.

Problem with pulling cams on these bikes is the necessity to replace the cam chain since they're not sectioned. All the other buckets rotate fine with the exception of this one, and I was thinking maybe it was due to heat on that cylinder.
I was able to pull the shim, with much cursing since the notch is nearly parallel with the exhaust cam.

 

[Steve]

You can pull the cams without replacing the chain. :-k

Just be sure to fasten something to the chain so it does not fall all the way down.

Remove tensioner.
Remove idler.
Remove intake cam.
Remove exhaust cam.

Install is the reverse, but be sure to time it correctly.

.

 

[fallous]

Guess it just didn't seem especially obvious how to easily remove it when I had to pull a friend's head and cylinder (yay for rusted piston rings on neglected barn bikes).

 

[bwringer]

Guess it just didn't seem especially obvious how to easily remove it when I had to pull a friend's head and cylinder (yay for rusted piston rings on neglected barn bikes).

http://www.repairmanual.com/catalog/H536

Pulling the camshaft ain't hard, and doesn't require replacing anything. Any mannual will have a clear, detailed procedure.

But if it's stuck as you describe, you very likely won't be able to remove the bucket without extreme measures (which will destroy the bucket). I normally use a small suction cup to ease the buckets out, and this probably won't work if it's stuck.


I wonder if it's simply sticky with cooked oil. Perhaps a few drops of PB Blaster along the edges of the lifter could help free it up. I'd try that repeatedly for a few days before pulling the camshaft. Drip some PB Blaster around the edges and rotate the engine a couple of turns to work it in.

You might also try warming the cylinder head around the bucket with a heat gun, although this could be pretty difficult -- a cylinder head is an excellent heat sink.


But frankly, if it's not sticking or making strange noises when you rotate the engine, and you don't see evidence of galling or scraping, I'd be inclined to leave it in place. Sometimes the buckets warp slightly, making them nearly impossible to remove or reinstall, but they work fine if you leave them alone.




If you need a good used bucket, PM me -- I have several leftovers.

 

[jpaul]

My dad had a bucket that wouldn't rotate on his 2001 GS500E. It ended up busting a valve on cold morning. I believe he got around it by swapping buckets around in the head to find a combination whose tolerances allowed free movement of all the buckets.