compression check

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10 Oct 2006 07:02 #83150 by TODDZ
compression check was created by TODDZ
What is the proper way to check the compression on my 78 kz650? and what is acceptable ?

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10 Oct 2006 07:10 #83154 by steell
Replied by steell on topic compression check
Engine warm and all sparke plugs removed with throttle held wide open is the way I do it, others say to remove one plug at a time.

135-150 psi is good, over 100 psi is usually acceptable, under 100 psi normally means there is a problem.

It's a good idea to check/adjust the valve clearances first, as they can have a significant effect on compression.
KD9JUR

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10 Oct 2006 07:42 - 03 Dec 2008 12:09 #83164 by JMKZHI
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Last edit: 03 Dec 2008 12:09 by JMKZHI.

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11 Oct 2006 08:19 #83446 by TODDZ
Replied by TODDZ on topic compression check
Thanks I did the check 175,175,175,175 psi

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11 Oct 2006 08:39 - 03 Dec 2008 12:11 #83451 by JMKZHI
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Last edit: 03 Dec 2008 12:11 by JMKZHI.

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11 Oct 2006 10:21 #83465 by TODDZ
Replied by TODDZ on topic compression check
I Got 175 psi on each cylinder.

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11 Oct 2006 10:31 #83469 by TODDZ
Replied by TODDZ on topic compression check
yes ending numbers did I not check the othe numbers.

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11 Oct 2006 15:53 #83524 by steell
Replied by steell on topic compression check
Well, that's certainly not worth complaining about :D
KD9JUR

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11 Oct 2006 16:12 #83527 by Biquetoast
Replied by Biquetoast on topic compression check
On this topic, where can I get a good, relatively cheap compression tester?
(1.) '75/'76 KZ400D - Commuter
(2.) '78 KZ750B3 Twin - Commuter
(3.) '78 KZ750B3 Twin - Commuter
(4.) '75 KZ400D - Sold
kz750twins.com

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11 Oct 2006 17:55 - 03 Dec 2008 12:11 #83541 by JMKZHI
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Last edit: 03 Dec 2008 12:11 by JMKZHI.

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07 Jul 2007 08:47 #155301 by KaZooCruiser
Replied by KaZooCruiser on topic compression check
steell wrote:

Engine warm and all sparke plugs removed with throttle held wide open is the way I do it, others say to remove one plug at a time.

135-150 psi is good, over 100 psi is usually acceptable, under 100 psi normally means there is a problem . . .


I have a question:

If atmospheric pressure is 14.7 (at sea level?), and the compression ratio is 9.5:1 (stock factory spec),

anything above @ 140psi seems indicative of a problem.

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09 Jul 2007 09:20 #155658 by dnpurdy
Replied by dnpurdy on topic compression check
yeah, that's an interesting thought. Can you safely assume that the pressure in the cylinder when the intake value closes is atmospheric?
(1980 KZ440-A1 sold project bike)
(1982 KZ750-N1 still stolen)
1982 KZ750-N1, my only now

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