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compression test vs leakdown

  • Thread starter Thread starter gssuzukixxx
  • Start date Start date
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gssuzukixxx

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The compression on my '77 GS750 (converted to 850) is 105 to 110 psi on all cylinders when engine is warm. I just did a leakdown test using a DYI test setup that gave 10% leakage on one cylinder. Is that leakdown consistant with those compression readings?

Thanks
Brian
 
OK I'm thinking the compression numbers are low but the leakdown is not too bad.

What do you guys think?

BTW for the compression test the bike was warmed up the throttle wide open.
 
Did you have the throttle wide open when you took the readings? If not, that will lower the readings.

EDIT: Just read that you did this....

Ride the hell out of it....
 
Suzuki mad said:
Whats the reading when cold?
Click to expand...

Warm of cold doesn't seem to make a difference to leakdown or compression readings.

During the leakdown test the only air I hear escaping is at the crankcase oil filler so that would indicate rings. But you don't hear much leakage and the 10% leakdown doesn't seem too bad to me (comments?).

I could ride the hell out of it but I have put about 1000km on the bike since the new rings so I am not sure how much more breakin will take place now.

The thing is that the bike runs real nice, doesn't use hardly any oil and the oil stays clean. If you were getting blowby past the rings wouldn't you expect the oil to get dirty fast?

I read elsewhere that if you have low compression but low leakage then your valve timing might be off. I have checked it and it I did it right but I was wondering if the "T" notch would be off from TDC. So the next thing I was going to do is make a piston stopper and establish TDC independ of the marks. I know I am grasping at straws here.

It is just psychological thing; I keep thinking that there is a whole bunch more performance to be had if only the compression were higher.

Brian
 
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