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compression testing
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compression testing
I checked the compression in the cub today, varied from 95 to 80. i did it with all 4 plugs out and the choke pulled. Is this the right way to do it? Thanks
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- 10+ Years
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Re: compression testing
Hi Rob, compression should be checked with all plugs out, throttle open, check it cold then hot, note the difference if any, after a dry test give it a squirt of oil in the cylinders, then retest, if there is a large difference in readings wet and dry it shows the rings worn
Tim
Tim
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- 10+ Years
- Posts: 2729
- Joined: Sun Oct 03, 2004 7:11 am
- Zip Code: 03848
- eBay ID: panelbeata
- Tractors Owned: 1947 circle cub
1950 cub demonstrator
1957 cub
1967 cub - Circle of Safety: Y
- Location: NH, Kingston
- Contact:
-
- 10+ Years
- Posts: 2729
- Joined: Sun Oct 03, 2004 7:11 am
- Zip Code: 03848
- eBay ID: panelbeata
- Tractors Owned: 1947 circle cub
1950 cub demonstrator
1957 cub
1967 cub - Circle of Safety: Y
- Location: NH, Kingston
- Contact:
-
- 10+ Years
- Posts: 5184
- Joined: Tue Jan 12, 2010 2:08 pm
- Zip Code: 12514
- Circle of Safety: Y
Re: compression testing
cylinders should all read within 10% of each other,if it is over 90 it is probably ok, nice and tight around 125 lbs, they will run on less, I have seen them with 50 lbs and run but not much power
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Re: compression testing
Anything within 10% difference between high an low is considered acceptable. 70 to 80 psi is getting on the low side.
I'm more concerned with cold engine psi, dry test. Looking for the 10% difference.
I would do the dry test again with a dead cold engine, then a wet test on the dead cold engine.
The tractor with 80 to 95 psi per cylinder will still pull a plow or mow. I used my Cub after initial purchase with slightly lower psi numbers for two years - until I rebuilt the engine.
I'm more concerned with cold engine psi, dry test. Looking for the 10% difference.
I would do the dry test again with a dead cold engine, then a wet test on the dead cold engine.
The tractor with 80 to 95 psi per cylinder will still pull a plow or mow. I used my Cub after initial purchase with slightly lower psi numbers for two years - until I rebuilt the engine.
I have an excuse. CRS.
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