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Old 02-13-2019, 03:53 AM   #16
Join Date: Nov 2018
Posts: 57
Default Re: Low Compression - keep trying or rebuild?

Originally Posted by pokey View Post
... Currently compression (in psi) on cylinders 1 to 8 is 70, 65, 40, 35, 40, 60, 42, 25.
Compression ratio is calculated as 15 divided into compression psi pressure. An 8:1 cylinder would be 120/15. An 6:1 cylinder would read 90psi. You highest reading of 75psi means CR of 5 ??? If I recall correctly it takes a CR of 4 to ignite the gas. So either you have a not really working engine or a bad pressure gauge. More likely the latter.

Borrow a friends gauge and make certain you have a fully charged battery and turn the starter over for 4-5 revolutions and get new readings.
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