compression check

TODDZ
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compression check

10 Oct 2006 07:02

#83150

What is the proper way to check the compression on my 78 kz650? and what is acceptable ?

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steell
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Re: compression check

10 Oct 2006 07:10

#83154

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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JMKZHI
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Re: .

10 Oct 2006 07:42 - 03 Dec 2008 12:09

#83164

del

Last edit: 03 Dec 2008 12:09 by JMKZHI.

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TODDZ
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Re: compression check

11 Oct 2006 08:19

#83446

Thanks I did the check 175,175,175,175 psi

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JMKZHI
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11 Oct 2006 08:39 - 03 Dec 2008 12:11

#83451

del

Last edit: 03 Dec 2008 12:11 by JMKZHI.

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TODDZ
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Re: compression check

11 Oct 2006 10:21

#83465

I Got 175 psi on each cylinder.

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TODDZ
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Re: compression check

11 Oct 2006 10:31

#83469

yes ending numbers did I not check the othe numbers.

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steell
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Re: compression check

11 Oct 2006 15:53

#83524

Well, that's certainly not worth complaining about

KD9JUR

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Biquetoast
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Re: compression check

11 Oct 2006 16:12

#83527

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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JMKZHI
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Re: .

11 Oct 2006 17:55 - 03 Dec 2008 12:11

#83541

del

Last edit: 03 Dec 2008 12:11 by JMKZHI.

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KaZooCruiser
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Re: compression check

07 Jul 2007 08:47

#155301

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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dnpurdy
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Re: compression check

09 Jul 2007 09:20

#155658

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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