Won't start in cold weather

[Eugene]

Add about one tablespoon to the top of each piston, roll the engine over a couple of times, and then take the compression tests again.

Actually you should have started with a dry test, without the oil.

The test results are uneven for sure. Should be/looking for less than 10% difference between high and low numbers.

[Ihandy]

This morning I tried a new compression test following the correct procedure these are my results at about 20° today I started with the dry test with the number one cylinder at 50 psi number two cylinder 65 psi number 3 cylinder 65 psi and number four cylinder about 52 psi then I did the wet test and the number one cylinder was at 55 psi The number two cylinder was at 85 psi a number three cylinder was at 105 psi and the number four cylinder was that 115 psi it shows me the number one and two cylinders are very low I noticed a wet spot on the intake by the one and two cylinders going to try new manifold gaskets next maybe that will boost my compression and get the gas to where it's needed any other thoughts would be appreciated

[69ranger]

Opinions vary, but here are my 2 cents worth. Your test kind of confirm that your engine may not be in the best condition. Low compression will cause hard starts, in extreme temps, both hot and cold. So you may want to think about a rebuild in the future.
So does the engine smoke? Have blow by out of the dip stick tube? This is a window into the condition, as well..

A hot blue spark is a must, regardless of engine condition. I have found a good hot magneto, rather than a distributer to help the old 6 volt systems to start better, as you have no loss in voltage, when cranking.

As was mentioned, updraft carburetors, 6 volt systems and the flat head design, all hinder these engines, both in performance, and starting in cold weather, and low compression does nothing but make this worse

A cub with an engine in decent condition, and the ignition in good shape, should start pretty dependably at temps down to the teens or even lower. Our cubs generally do, but if colder and 8 or 10 degrees, I usually give them a little whiff of either, down the air intake.

Good luck with your tractor.

[staninlowerAL]

Other possible causes: valves might benefit from adjusting clearance and carbon buildup on the weak cylinders. Check all for correct clearance and if that does not help you might have to remove the head to clean up the valves and seats. If you remove the head, check the valves and seats for pitting and burning. Both conditions can be repaired. IMHO

[Eugene]

going to try new manifold gaskets next maybe that will boost my compression

Compression takes place inside the cylinder. Manifold gaskets are outside the cylinders and won't make any difference in compression.