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Valve clearance confusion - 78 GS750E

  • Thread starter Thread starter sclark900
  • Start date Start date
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sclark900

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First off, thanks to this forum for the bounty of information on the Suzuki GS series! I'm in the process of rebuilding a 1978 GS750E and have referenced the site often.

I currently have it torn down to the frame w/ the engine out. Last night I pulled the head in order to replace the head gasket and possibly rings. Prior to doing that, I checked all the valve clearances and cataloged all the shims. I followed the manual (and bikercliff's guide) which state the cams should be either perpendicular or horizontal to the head when checking clearance. However, when I did so, I noticed that I got different numbers for each position. See attached spreadsheet which shows the numbers. Is this normal? I found it a little odd. If normal, I'm assuming I would adjust against the lowest value to insure at least minimum clearance tolerance. Lastly, I also noticed that when aligning the cams, when using the crank indicator to find TDC incicated w/ a T, the cam lobe would be just a bit shy of horizontal and/or vertical. Is that normal? I measured the valve clearance for both and found no difference.

Note - my feeler gauge only goes to .04mm, so clearances marked in red w/ .03 on the attached chart assumes clearance is too tight. I realize .03 is w/in tolerance, but I prefer to err on the side of caution.

I have a few other questions regarding compression, but one at a time! Any help would be appreciated.

Valves.JPG
 
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Those variations may be caused by cam wear. The effect of the opening and closing ramps shouldn't be influencing readings in those regions. I set my clearances when the toe is furtherest away from the shim, i.e., dead in line with the valve stem axis.

There will be some minor wear on the lobes as the mileage of the bike increases. This is noticeable on bikes that have spent a lot of time idling on the side stand.
 
Adjust the valves per the Suzuki method. It's not mix and match for cam position. You need both adjacent valves on the base circle otherwise one of the valve will be pushing up on the cam and skewing it within the journal clearance, thus messing up the readings.
 
Nessism said:
Adjust the valves per the Suzuki method. It's not mix and match for cam position. You need both adjacent valves on the base circle otherwise one of the valve will be pushing up on the cam and skewing it within the journal clearance, thus messing up the readings.
Click to expand...

I was having the same problem that you are having, until I followed Ed's advice. Do it per the Suzuki manual. The method 49er mentions is what the Clymer manual states, and it is wrong. Lots of people have fallen into this mistake.
 
Excellent. Thanks for the info. Much appreciated.

So if I understand correctly, would it be safe to say that I should be taking the measurement from the 'B' - horizontal cam position?

jsandidge said:
I was having the same problem that you are having, until I followed Ed's advice. Do it per the Suzuki manual. The method 49er mentions is what the Clymer manual states, and it is wrong. Lots of people have fallen into this mistake.
Click to expand...
 
sclark900 said:
Excellent. Thanks for the info. Much appreciated.

So if I understand correctly, would it be safe to say that I should be taking the measurement from the 'B' - horizontal cam position?
Click to expand...

Position 1E cam lobe in B position and adjust 1E & 2E
Position 4E cam lobe in B position and adjust 3E & 4E

Position 1I cam lobe in A position and adjust 1I & 2I
Position 4I cam lobe in A position and adjust 3I & 4I
 
Yet another invitation here to follow the procedure in the Suzuki manual.
With EX1 in the forward position, EX2 will be UP. Measure BOTH, EX1 and EX2.
Rotate the crank 180 degrees (1/2 turn), you will see IN1 pointing UP and IN2 pointing back. Measure BOTH, IN1 and IN2.
Rotate the crank another 180 degrees, you will see EX4 pointing forward and EX3 pointing UP. Measure BOTH, EX4 and EX3.
Rotate the crank a final 180 degrees, you will see IN4 pointing UP, IN3 pointing BACK. Measure BOTH, IN4 and IN3.

May I also interest you in another spreadsheet for figuring your shims?
It also helps you keep track what's in there from one time to the next.
Information is in my signature.

.
 
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