Bad Vibrations

[raistian77]

The fact that it was too tight. If you look through the spark plug hole while the valve is open, a good valve will have a silver circle where the valve contacts the seat. If you look at one that has been run too tight, there is no silver ring, it hasn't really been contacting the seat. You adjust the clearance, now it can close. But the sealing surface is a little messed up, not sealing as nice as it should. Maybe it's even burnt just a tiny bit. After the valve closes a few million times, that seal starts to get better, forms the silver ring again, the valve sinks into the seat a tiny bit further, the compression gets better. As it does, the clearance gets tight again. Not sure if my reasoning is correct, but they usually do improve, and they usually need a few valve adjustments along the way. I have seen this happen on four GSes this summer, probably will see the improvement on a few more once I get them on the road. Valves were too tight, adjusted them, the compression came up. They almost always get better with miles, and need a few adjustments along the way. Had a guy here today, shop told him it needed a rebuild, due to bad compression. Adjusted the valves, got 115, 115, 116, 115.
(Low numbers due to the elevation here, at sea level they would all be in the 130s)


Of course, if the valve has been burnt too much, it will never improve, but if that was that bad it wouldn't have come up to 100 psi right after the first adjustment.

ok, so my next step will be to mail off the shims I have to the club and get what I need to make all the adjustments to the loose side and put some more miles on it and see what happens.

Also oil added to the cylinders does nothing to the compression numbers.

 

[tkent02]

ok, so my next step will be to mail off the shims I have to the club and get what I need to make all the adjustments to the loose side and put some more miles on it and see what happens.

Also oil added to the cylinders does nothing to the compression numbers.

Great, your rings are fine.

 

[Steve]

Dang, I should have asked Steve to test run it when he was here

I can stop on my way home, but that won't be until mid-November.

The service manual states to check with cam lobe straight up, prefered or intake straight back and exhaust straight forward. I did mine all straight up.

That is the Suzuki method in the service manual

Straight up or to the rear for intake
Straight up or to the front for the exhaust

Not quite, one of the pair up, the other forward. Measure them both at this position. So for instance, measure #3 and #4 exhaust at the same time, one lobe up, the other forward....
Maybe that's what you meant?

I usally check twice, once lobes up than pointed staight.

As tkent mentioned, you set the cam lobes on one side so that both lobes are at about 45 degree angles to the valve. On the exhaust side, that would be one lobe forward, the other one up. Without moving the cam, measure BOTH valves. Because neither lobe is pushing on a valve, the cam is centered in its bearing, so you can get accurate, repeatable readings. I did not ask you about details on your adjustment process, I just assumed it was done correctly.

I usually start with exhaust 1&2. Check both of them, rotate the crank 180 degrees, check exhaust 3&4. Rotate another 180, check intake 1&2. Rotate another 180, finish up with intake 3&4. Actual starting point does not really matter, but the progression will be the same.

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[raistian77]

I can stop on my way home, but that won't be until mid-November.







As tkent mentioned, you set the cam lobes on one side so that both lobes are at about 45 degree angles to the valve. On the exhaust side, that would be one lobe forward, the other one up. Without moving the cam, measure BOTH valves. Because neither lobe is pushing on a valve, the cam is centered in its bearing, so you can get accurate, repeatable readings. I did not ask you about details on your adjustment process, I just assumed it was done correctly.

I usually start with exhaust 1&2. Check both of them, rotate the crank 180 degrees, check exhaust 3&4. Rotate another 180, check intake 1&2. Rotate another 180, finish up with intake 3&4. Actual starting point does not really matter, but the progression will be the same.

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I will recheck once I get some shims in, I don't think it will be to much diffrent than the reading I got today. In a car there is no point where the cam is not pressing down on a valve, but there are more than 2 caps on em also lol