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Valve shim clearance advice needed

  • Thread starter Thread starter Suzuki_Don
  • Start date Start date
S

Suzuki_Don

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I am working on a cylinder head for a friend. It is off a GS400 - I have posted here to obtain more responses.

I have had the seats re-cut, the valves faced and guides replaced. Now I find that on the intake side when I have my smallest shim installed on both the intake and exhaust bucket I have zero clearance. The shim I am using is a 2.25mm.

Is there any way to work out how much I need ground off these valve stems without having some spare shims ground down to 2.15mm or less? It is possible I could have the shims ground down to 2.15mm and there is still no clearance.

Suggestions and guidance please?

Thanks
 
First I wouldn't grind shims below the thinnest available. There is probably a good reason to have a minimum.
Second you could well have negative clearance now and will need to find something thinner to put in to open the gap and give you something to measure. Maybe you will need to sacrifice a shim and grind it down. Then you have a starting point to grind off the valve stem. Just ensure whoever is doing the grinding knows the difference between flat and square. I've seen a few shims come out that were not. Check the valve height as well , they could have been ground before.
 
With cam lob away from bucket /shim, remove shim. Use a washer (or steel flat stock,etc) of known size, like 1.5 mm thick ,stick in bucket and then use your feeler gauges to determine what the combined distance is between bucket and cam. This will put you in ballpark for determining how much to grind off stem.
 
Yep, the solution is to have the valve stem ground down to compensate for the amount of material removed from the valve seat. Pretty standard practice when having the valves seats ground.
 
1.580" from the tip of the valve to the bottom of the tappet bore ( no spring base ).
 
Thanks Jay for a valuable contribution.

At this stage I have removed the two shims in turn and substituted a 1.65 hardened steel washer and recorded the clearances. I am now midway through working out the maths to see how much needs to be ground off each stem. When done I will remove the cams and valve springs, etc. and take the measurement as explained by you. And compare the difference.

The thing I find a headache is removing the valve stem oil seal every time the lower spring seat has to come out.

Thanks again Jay. Great technical knowledge.
 
Didn't know they made a GS400 /4 My spec was for the twin. So my question is, why was the valve stem height not noted during tear down?
 
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