Compression
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Stage I
Joined: Jul 2021
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From: OH
Compression
81 strugglehead with electronic ignition. Check compression cold 90 in the rear 100 in the front. Check compression hot 90 in the front 100 in the rear. What's up with that?
Can't find what the compression should be in my Clymer manual. I read somewhere that the Harley manual says anything 90 and up and both within 30 lb is okay.
Can't find what the compression should be in my Clymer manual. I read somewhere that the Harley manual says anything 90 and up and both within 30 lb is okay.
Last edited by Toastmaster; Jul 12, 2021 at 10:34 AM.
Road Captain
Joined: May 2015
Posts: 554
Likes: 359
From: Bristol, CT
81 strugglehead with electronic ignition. Check compression cold 90 in the rear 100 in the front. Check compression hot 90 in the front 100 in the rear. What's up with that?
Can't find what the compression should be in my Clymer manual. I read somewhere that the Harley manual says anything 90 and up and both within 30 lb is okay.
Can't find what the compression should be in my Clymer manual. I read somewhere that the Harley manual says anything 90 and up and both within 30 lb is okay.
Clymer manual page 8&9. Doesn’t say that these are the values / specs. I’ll have to recheck my factory 78 1/2 - ‘84 service manual but I’m 180 miles from home. I took the Clymer 1959-79manual to read up in that POS front brake.
someone here will give you more info.
I’m getting a ‘76 FXE on the road and my readings were no more than 100 ea cyl. I have other issues to sort before the engine/primary /trans rebuild what ever is needed.
Seasoned HDF Member
Joined: Nov 2006
Posts: 12,878
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From: la la land jerzey
Every compression gage is different and the speed that the engine is moving when checking comes into play
the one we use a combo compression and leak down by snap on - those numbers you can take to the bank
but you need to do both to. Be sure -
what you have in 90 / 100 hot or cold is fine again if your using a china copy of a walmart gage then who knows
the one we use a combo compression and leak down by snap on - those numbers you can take to the bank
but you need to do both to. Be sure -
what you have in 90 / 100 hot or cold is fine again if your using a china copy of a walmart gage then who knows
Tourer
Joined: Sep 2020
Posts: 487
Likes: 289
From: Northern MN
WTF, this is the Shovelhead forum. Not good enough???
Hell if you google the question half the time it comes back to this forum.
Why should a guy not ask a question here. What is the f##cking forum for?
Tom
Hell if you google the question half the time it comes back to this forum.
Why should a guy not ask a question here. What is the f##cking forum for?
Tom
Road Master
Joined: Jun 2006
Posts: 905
Likes: 207
From: Minneapolis
I googled it - here ya go
"For example, if the atmospheric pressure is 14.7 psi and the compression ratio is 11:1, the equation to solve for the psi is (14.7*11)/1. Therefore, the answer is 161.7 psi. People use this method of calculation to determine the pounds per square a piston produces."
"For example, if the atmospheric pressure is 14.7 psi and the compression ratio is 11:1, the equation to solve for the psi is (14.7*11)/1. Therefore, the answer is 161.7 psi. People use this method of calculation to determine the pounds per square a piston produces."
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