Valve Clearances

[xssidecar]

HI all,
I need a bit of advice regarding valve clearance adjustment on my 1980 XS1100.This job is taking a while as I have a lot of other commitments and it's been several months on the go.I finally got the new pistons fitted and the head bolted down,cams in and everything lined up nicely.
Now to the problem.I fitted four new inlet valves after having the guides replaced and the valve seats matched to the new valves.
I began checking the existing clearances prior to reshimming.The exhaust clearances were simple to check but when I came to checking the inlet clearances I cannot get even a 0.04mm feeler guage in let alone a 0.16mm.In effect I have no useful clearance at all.
I have ideas why this might be but am a bit unsure how to solve the problem.
I'm guessing that the fact the enginneer cut the seats after putting in the new guides has raised the valves a bit higher.Any suggestions will be appreciated.
Thanks
xssidecar

[crazy steve]

All you can do is drop the shim size about four sizes, then re-measure. If you go below the minimum shim size available, then you need a new head....

[tarzan]

You could also take the shims to a machine shop and have them ground to the needed thickness.Or possible grind the end of the valve stems.

[natemoen]

If you go below the minimum shim size available, then you need a new head....

Or you could do what Yamaha should have done in the first place and have hardened valve seats put in.

If you want to spend that kind of money on it that is.

[crazy steve]

You could also take the shims to a machine shop and have them ground to the needed thickness.Or possible grind the end of the valve stems.

Awful lot of unknown consequences involved in grinding the shims; can you get the same surface finish? Will that remove the hardening? And do you really want to repeat this process the next time the valves need adjusting?

And you can't grind the ends of the valves any meaningful amount. Doing so will cause the shims to work against the shim bucket, not the valve and you'll have the valve retainers fail....

The FSM is clear on this; once you run out of adjustment, replace the head...

[Ken Talbot]

Awful lot of unknown consequences involved in grinding the shims; can you get the same surface finish? Will that remove the hardening? And do you really want to repeat this process the next time the valves need adjusting?
.....

If you go this way, grind the face that has the number printed on it as that is no longer going to mean anything anyways. Use an engraver to mark its new size, and install that side into the bucket. This way, you don't mess with the surface finish or hardening of the part that rides against the cam.

With a bit of care and patience, you can grind the shims by hand by lapping tham on a piece of wet/dry sandpaper affixed to a sheet of glass to act as a flat lapping plate.

Edited - obviously the shim rides against the cam, not the velve stem!

[TomB]

I've owned my original XS11 for 30 years and have done 80K miles on it, it still has the 8 original shims in it that it came from the Yamaha factory with, they're smaller than they were when new because I've been grinding them down all these years when adjustment was needed.

I was a Toolmaker for 18 years so this was a simple task using a surface grinder, and enabled me to get clearances exactly correct, not just the next shim size down. I hardness tested them on both sides and again after grinding and found no difference, they're not hard, more toughened, I can't remember the figure exactly but it was somewhere in the low 50's Rockwell C scale. I prefer shims softer than my cams, shims can be replaced cheaper.

There is no wear on cams or shims in that 80K miles.

Go for it I say.

[motoman]

Or you could do what Yamaha should have done in the first place and have hardened valve seats put in.

If you want to spend that kind of money on it that is.

Already came from factory with hardened seats due to unleaded fuels, AND was one of the selling points at that time.

[tarzan]

Surface grinding gives excellent finish,and your shims would be good for quite awhile.

[natemoen]

Already came from factory with hardened seats due to unleaded fuels, AND was one of the selling points at that time.

Steel valves against aluminum head is not the best of enginering ideas.

I am talking have new steel seats put in to bring the valve back out close to its oringinal position.

[motoman]

Steel valves against aluminum head is not the best of enginering ideas.

I am talking have new steel seats put in to bring the valve back out close to its oringinal position.

Oh....well thats different from what was first stated.

[crazy steve]

...I was a Toolmaker for 18 years so this was a simple task using a surface grinder, and enabled me to get clearances exactly correct, not just the next shim size down. I hardness tested them on both sides and again after grinding and found no difference, they're not hard, more toughened, I can't remember the figure exactly but it was somewhere in the low 50's Rockwell C scale. I prefer shims softer than my cams, shims can be replaced cheaper..

This is different than grinding the shims below the 2mm minimum that Yamaha decided on. At what point below that thickness do you need to start to need worrying about shim integrity/durability? Have a shim fail and come out of the bucket and that's the end of your motor....

[TomB]

Thats a good question Steve, a ground down rigid shim (obviously if ground so thin its flexible its waaaaay too thin) coming out is very difficult to do when running engines at normal engine operating speeds, and if you do have one come out you'd be extremely unlucky to wreck any more than the head/valves, and the alternative for XSsidecar is a new head anyway.

A good question that is worth investigating, so he needs to remove the shims and use feeler gauges to find out how near to the 2mm minimum his shims need to be, if they're a whole lot under then other ways of reducing the valve may need to be looked at like grinding the valve stem as you suggest.

[crazy steve]

...if they're a whole lot under then other ways of reducing the valve may need to be looked at like grinding the valve stem

You can't grind the valve stem, that's the problem. As designed, the end of the valve is very slightly above the 'lip' in the bucket the shim seats on. Too high, and the shim will 'pivot' on the stem as the cam lobe travels across it. Too low, and the opening pressure will be against the bucket instead of the valve, leading to valve lock retainer failure. I know this for a fact, as I had a mis-machiined engine failure for just this reason.

There's multiple 'solutions', but all are difficult and/or expensive.

One, install new seats in the head. I'm not even sure this is possible given how close the valves are to each other and seeing how these weren't offered as service parts by Yamaha, would probably need to be custom parts. I believe the originals were cast into the head during manufacture.

Two, have new cams ground with a smaller base circle. But this will increase cam/shim/guide wear.

Three, have new, shorter valves made. Whatever amount you remove from the stem length, you'll have to relocate the stem lock grooves down by the same amount. You'll want to check for coil bind, maybe machine the spring pockets deeper into the head.

Of the three, if I were forced to choose I'd go with the last one. But I'm sure these custom made valves would cost far more than finding a good used head would.

[MPittma100]

Do It The Right Way The First Time

That's easy for me to say isn't it? Not too happy with the idea of grinding (modifying) shims to correct this issue.

What should have happened is that your machinist, that reworked the head, should have already adjusted the valve lash prior to giving it back to you.

He should have asked you for the camshafts, followers, and shims along with the head. He then would have ground the tips of each valve to correct all of the valve lashes. Tips can be ground to correct the lash without causing failure as long as it is done within reason. The shop I use shop does it every day. This procedure would have completely eliminated any need to adjust lash when the head was installed. I am very surprised that he did not do this.

If you cannot resolve with smallest shim, I would recommend removing the head and taking it back to that shop and let him finish the job.

Be careful not to bend any valves. It is easier to do than you may think. Good Luck.

MP