GS850 valve clearance: Cam lobe position

[Steve]

This skewing is only .001 or .002 but that's enough to throw off the measured readings.

Stock clearance is .03-.08mm but shooting higher is a safe bet.

Do the math on the stock clearance, you will find that it is .0012 to .0031". That means that the amount of the skewing is over half of the allowable range. Shooting for the larger end of the range is better (in more ways than one).

I even removed number 2 shim whilst checking clearance on number 1 in different planes so as not to have an altered reading due to "loading" forcing the came upwards.

Hopefully you did not rotate the crank while the shim was out. The edges of the cam lobe will be chipped by the edges of the bucket.

I do feel that with no loading from an adjacent lobe that the back of the cam is best place to measure and can understand that if doing two at once as per the procedure one would need to adhere to the written procedure or one of the two will be away from optimum measuring points.

There is no "optimum place" on the cam LOBE for measuring clearance, you have to look at the ENTIRE CAM. You mention removing a shim to remove any loading on an adjacent lobe. That is SO easily accomplished by simply positioning the lobes as described above, with both lobes on that side of the cam pointing away from their respective valves at about a 45° angle, so neither one is pushing against a spring.

Hopefully you see this as an "Ahaa" moment, recognize its simplicity and move on.

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[hannibal]

I'll take a stab at it. If you check as described (just an example) with 1 pointing vertical and 2 pointing horizontal, neither 1 nor 2 is activating the valve. If you try to check with 1 pointing horizontal, 2 is now activating the valve. If you try to check with 2 pointing vertical, 1 is now activating the valve.

If an adjacent lobe is activating its valve, your measurement will be inaccurate. The only way to measure correctly is with 1 and 2 not activating the valve. The only time 1 and 2 are not activating a valve is when 1 is vertical and 2 is horizontal.

[Steve]

The only time 1 and 2 are not activating a valve is when 1 is vertical and 2 is horizontal.

That would be true for the INTAKE cam.

For the EXHAUST cam, 1 would be FORWARD (horizontal) and 2 would be vertical.

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[hannibal]

That would be true for the INTAKE cam.

For the EXHAUST cam, 1 would be FORWARD (horizontal) and 2 would be vertical.

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It was an example.

[Grimly]

I will say this; in the first few years of owning GSs I always did it the traditional way, against the heel of the cam. However, I always shot for the wide end of the clearance allowable, so it wasn't a problem. As I've pointed out before, GS engines that are racking up tens of thousands of motorway (freeway) miles at steady speeds have almost zero valve train wear anyway, so it was even less of a problem for me.

[Steve]

It was an example.

No problem, but if you are going to give an example, at least let it be an accurate one.

The reason this one makes a difference is because the positions are different for the intake and exhaust cams.

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