My Compression Test results

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mva1958
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My Compression Test results

Postby mva1958 » Sat Jul 08, 2017 3:58 pm

Been reading a lot about compression testing lately, so I thought it was high time I performed one on my 1950 cub that I've had for 3 years. I use her mainly for mowing 2.5-3 acres of field (Mott FHC Flail mower) and for pushing snow/maintaining my 600' driveway. She's a bit of a smoker. Power has not been an issue but I have noticed a lack of what my dad used to call spizerinctum lately, hence the test. Oil consumption is not alarming, the oil level seems to sit at about halfway between the full and add marks on the dipstick.

I followed all the advice posted here (plugs out, starter off) about conducting the test EXCEPT I forgot to open the throttle all the way - it was about 2/3 of the way open, well above idle speed. Test was conducted with engine cold.

#1 100 dry/110 wet
#2 95 dry/110 wet
#3 110 dry/120 wet
#4 110 dry/120 wet

All's right with the world, right? The only thing that gives me pause is, I had trouble getting a solid reading on #2. On the dry test, the on the first try I got a reading of 60 - I didn't like that answer so I released the pressure in the gauge and hit it again - this time, I got 80 psi. I tightened the fitting in the spark plug hole a bit, did the test again, and got 95. Similar scenario with the wet test, first time 100, second time 110. Am I overthinking this? I might not have had a tight seal for the first dry test on #2, but I made sure I had one for the wet test.

I should have mentioned, I checked and adjusted the valves recently - they were pretty gummy. I set them to .013 like it says in my manual; I've since read that a lot of folks set theirs to .015. Does that make any difference?
If only Mrs. Hoyt and Mrs. Clagwell had gotten along...

Eugene
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Re: My Compression Test results

Postby Eugene » Sat Jul 08, 2017 4:16 pm

Compression test appear to be in the very good range. I would leave the engine alone.

No difference in engine performance between .013 and .015.

Might try some SeaFoam in the engine oil and gasoline. Thinking the piston rings are starting to stick in the grooves is causing the smoke.
I have an excuse. CRS.

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mva1958
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Re: My Compression Test results

Postby mva1958 » Sat Jul 08, 2017 4:22 pm

Thanks, Eugene - I shot some Seafoam in the carb intake and will add some to the oil/fuel as soon as I run to Napa to get some more.
If only Mrs. Hoyt and Mrs. Clagwell had gotten along...


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