Valve Clearances and Age.

Just wondering. Here's the 13mm shims I have in my freshly rebuilt GPz550 Head that I've just completed bench-shimming to get the .10-.20mm intake, and .15-.25mm exhaust the factory recommends:

#1 2.60(I), 2.05(E)
#2 2.65(I), 2.40(E)
#3 2.60(I), 2.45(E)
#4 2.55(I), 245(E)

The question is if that #1 Exhaust gap gets smaller as the head ages, and I have to replace that shim down the line, there's only one shim smaller, 2.00mm.

The rebuilt head only needed exhaust guides, everything else checked out, OK.

Thanks for your replies in advance.

Post edited by: CoreyClough, at: 2007/10/26 13:41

From the factory, all of the shims are usually in the 2.55~2.60 range on the early 550's. (I haven't opened an 84.) That 2.05 is worrisome. Why is it so different from the other 3?

After the first or second shim job 2.50~2.40 is normal.

You see my BOLD concern?

This is only a bench-shim, and maybe after I recheck later during engine break-in things might change for the better...I hope.

I think the only "easy" option you have (if a 200 is too thick) is to grind the valve stem. Not sure how having under-bucket shims affects that, but that's what I've done with one of my bikes with tight clearances.

I assume you checked to make sure the valve retainer is installed correctly and there isn't any foreign matter on the tip of the valve or under the bucket.

You could try to swap some buckets around and see if there is some variation there. But only swap the buckets if they move freely in the bore. Some buckets don't like to get swapped. But keep very good track of what came out of where.

...and as Skyman said, you can gain a little clearance by grinding the valve (or having a shop grind the valve). You only need about .1mm to buy you a good number of years.

Post edited by: loudhvx, at: 2007/10/26 14:35

Thanks, I'll see at the next clearance check. Under bucket valves would need the stem ground for larger clearances, and would need a thicker shim. Only time...

Does the 550 have a stem length spec? the 900/1000 do. As noted, could just be a long valve. There is also a spec for how much a valve can be ground. If you find that the valves can not be ground any as they are on the edge of spec, you will need to have a new seat pressed in... not sure if there are replacements for the 550 seats so you are looking at a different head in that case.

In the factory supplement manual, there is a note stating the following:
*Do not grind the valve stem end to repair it or to permit additional valve clearance.
*If the valve end is ground, the shim may contact the spring retainerand/or split keepers during operation, allowing the keeper to loosen. Consequently, the valve may drop into the engine, causing serious damage."

Looks like WG is right in that the valve would need to be replaced.

There is an added chart that is titled:

"Valve Installed Height"
-Inlet Height 36.09mm-37.01mm. Exhaust Height 36.04-36.96mm.
-Cause: Normal acceptable.
-Recommendations: After assembling check and adjust valve clearance.

-Inlet Height more than 37.01mm. and/or Exhaust more than 36.96mm.
-Cause: Valve face or seat worn out, or ground excessively.
-Recommendations:
1. Move valve to shallower cut seat. Remeasure.
2. Replace valve. Remeasure
3. Replace cylinder head. Remeasure.

Well at least I have options. Thanks for makinig me look into thie WG. I might as well finish all the information:

Measuring Valve Installed Height
*Install the valve in the cylinder head.
*Pushing up on the valve so that it seats firmly in the valve seat, measure the valve installed height with vernier calipers. The valve installed height is the distance from the bottom of the cylinder head lifter hole to the end of the valve stem.


For those that want the whole page to save the information, here it is:

Darn Double Postings. :S

Post edited by: CoreyClough, at: 2007/10/26 17:28