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compression test

  • Thread starter Thread starter bubby
  • Start date Start date
B

bubby

Guest
i did a compression test on my 77 gs 750 today and here are the numbers
1 135 lbs

2 137 lbs

3 142 lbs

4 136 lbs

was hoping for some insight on if these are good numbers or not
 
Good numbers

Did you do them engine hot with wide open throttle?

Adjusted your valves yet?
 
i adjusted the valves when i first got the bike 3 months ago but i didnot record valve shim sizes or compression so i dont have anything to compare these numbers. i remember number 3 cylinder had low compression and i put a thinner shim in the intake valve
(big t) i did the test cold the bike sat all night and i did it first thing thismorning
i did have the throttle wide open
 
It would be interesting and informative to see some hot compression numbers, as well as a "wet" compression test to give you an idea of the shape your rings might be in.

Those numbers are a little low but serviceable, at least as far as the 650 goes, but the variance is excellent. IIRC, the 650 service manual says that the head could use some servicing when all of the compression numbers are below 148 psi (at sea level).

I'd be pretty happy with the numbers the way they are, though.
 
77gs 750 manual says under 100 lbs needs servicing i am content with my numbers
 
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