Compression Check

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29 Nov 2010 15:46 #414682 by BIGKEVIN
Compression Check was created by BIGKEVIN
I have a 1976 KZ900 that I want to do a compression check on. What is the compression supposed to be on this year bike ?
1976 KZ900
2006 ZX6R

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29 Nov 2010 15:55 #414683 by MFolks
Replied by MFolks on topic Compression Check
On a new or rebuilt engine, you might see 180 PSI after a good break in. Engines will run at 100 PSI but will have little power.

Before doing a compression check, adjust the valve lash as having an open valve negates any compression testing.
1982 GPZ1100 B2
General Dynamics/Convair 1983-1993
GLCM BGM-109 Tomahawk, AGM-129A Advanced Cruise Missile (ACM)

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  • lemo32
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29 Nov 2010 16:03 #414684 by lemo32
Replied by lemo32 on topic Compression Check
I would want to see atleast 120 psi, on every cylinder, and no cylinder having more than a 10 PERCENT difference, 150 would be great, but as long as all cylinders are close you should be o.k.
1979 kz 1000 06 katana 750

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29 Nov 2010 16:34 #414696 by BIGKEVIN
Replied by BIGKEVIN on topic Compression Check
When checking the compression, are you supposed to have the throttle open or closed ?
1976 KZ900
2006 ZX6R

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29 Nov 2010 16:35 #414697 by andy9802gt
Replied by andy9802gt on topic Compression Check
open
'78 KZ1075 LTD
stage 1 head by Larry Cavanaugh
race built crank by John Pearson
Mikuni rs34's
k410 cams
back cut tranny
8" over D&G swinger
proving once again that age and treachery is better than youth and enthusiasm

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29 Nov 2010 16:39 #414699 by BIGKEVIN
Replied by BIGKEVIN on topic Compression Check
What would be the difference in the compression between the trottle being opened and closed ?
1976 KZ900
2006 ZX6R

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  • andy9802gt
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29 Nov 2010 16:51 - 29 Nov 2010 16:52 #414703 by andy9802gt
Replied by andy9802gt on topic Compression Check
my thought on it would be if you don't open the throttle you would not have enough air coming into the chamber to create positive pressure. with the throttle closed and the plugs in it would just evacuate the air in the cylinder creating a vacuum instead of pressure. I could be wrong though... :unsure:
'78 KZ1075 LTD
stage 1 head by Larry Cavanaugh
race built crank by John Pearson
Mikuni rs34's
k410 cams
back cut tranny
8" over D&G swinger
proving once again that age and treachery is better than youth and enthusiasm
Last edit: 29 Nov 2010 16:52 by andy9802gt.

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29 Nov 2010 16:55 #414704 by BIGKEVIN
Replied by BIGKEVIN on topic Compression Check
I was just wondering about the difference. I'll check the compression tomrrow. Thanks for the info.
1976 KZ900
2006 ZX6R

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30 Nov 2010 13:49 #414846 by steell
Replied by steell on topic Compression Check
BIGKEVIN wrote:

What would be the difference in the compression between the trottle being opened and closed ?


Depends, but the difference could be as much as 100 psi.
KD9JUR

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