Left Exhaust bucket only rotates 180 degrees

[Darkstar]

- The other three buckets rotate 360 degrees with the shims in, but this one only goes 180.
- The shim clearance for is 0.01mm, it starts rough, but runs pretty good after warming up.
- Finger/plughole compression test has strong suck/blow after it's warm, but very light when it's cold.
- User gsjack broke a valve this way riding in sub zero weather, but his bucket was stuck hard, maybe I'm approaching the same.

CHOOSE YOUR OWN ADVENTURE:

A. Relax, shim to 0.10mm clearance, ride on in to the night.
B. Relax, shim to 0.04mm clearance, ride on in to the night.
C. Worry that you'll break a valve stem, pay someone to work on the bucket issue, or think about a new bike.


EDIT: I just found my answers here in this thread: http://gstwins.com/gsboard/index.php?topic=49050.0

[Big Rich]

Have you tried taking the bucket out? You'll need to remove the cams of course. But if the bucket isn't spinning (somewhat) freely, then there's some type of interference.

And if you are concerned about compression tests, get a proper tool. GSJack's thumb has over 60 years of calibration! I know mine isn't calibrated yet.....

[Darkstar]

Reinstalling cams may be out of my league. Is it a serious problem if it's tight? I'm using my fingers and haven't tried pushing it around with a tool.

[the_63]

It can be a little fiddley getting the camshafts back in, I have two left feet for hands, and my dad says if brains were dynamite, I wouldn't have enough to blow my own head off 

Any way, I switched out my exhaust camshaft and did all the work myself.

https://www.youtube.com/watch?v=6X0VwcdZq7M&t=6s
https://www.youtube.com/watch?v=KmfkhLE0Cog

These have all you need to know 

How hard can it be 

Chris

[Darkstar]

Very nice of you to share this with me, i may just give it a try.
Do you happen to know why the tappet follower (aka as "bucket") must rotate? Here's my thinking: the camshaft wears on the shim surface, but not on the bucket itself. If it didn't rotate the cam would dig grooves into the shim surface as it sat in one place. the bucket also needs to slide up and down to move the valve, and this if got stuck in place the exhaust valve stays open and gets cooked.

Also, I see no mention of testing rotation of these in neither the service manual nor haynes. I want to be sure im headed down the right road before I start removing the camshafts. I may just clear the oil and flush it with solvent, like acetone, to see if some crud got caught in there preventing movement. anyone know not sure if buckets require assembly oil/moly during installation?

[Atesz792]

AFAIK, the valve seat wears, not the camshaft, but otherwise I think you're right.
Rotation is necessary for the camshaft and the shim too, so they don't wear each other out prematurely.

[The Buddha]

Everything wears man. I've had a scratch on my camshaft that over 40K miles I saw it get fainter and fainter.
GSJack broke a valve cos it was hanging up in the guide. Or hang the bucket in the borehole. You're not rotating in at the top of the valve = not the same thing.
Imagine the bore it slides in as a piston, the bore should be a cylinder, there was a constriction making it stuck there.
You wont have that issue, if you get yours right enough to be an issue, your bike wont even crank.
Or I guess you may break a bucket. Likely you're not gonna break anything if it will not rotate but move up/down OK.
BTW your valve clearance could just be too tight, or the shim is lop sidedly worn.

Cool.
Buddha.

[Darkstar]

Cool.

I took the shims out and they are indeed level, and with only surface wear, and yes the clearance is tight, like 0.02mm. New shims are en route. Today i did my first warm open throttle compression test: 145psi on right, 135 on the left, barely passing the spec. Once the shims arrive I'll put them in and test again. If the numbers go up, you'll be hearing from me about the jet order  This winter has been so warm that I figure I might as well do the whole job.

[Darkstar]

UPDATE:

Well, I was wrong, because this bucket rotates just fine. Either my shim tool was pushing up against the bucket, or my cams weren't aligned right last time I did this. What a relief. Thanks for the sanity check. And for anyone pulling shims, I found the easiest way to do it is glue a small rare earth magnet to the end of a paintbrush, and just slide it in after you tilt the shim up, picks it out real easy.