Hi,
Here is info for doing a compression test, if you need it.
Open the throttle fully to do the compression test, so the engine can get air.
Have all 4 spark plugs out of the engine at the same time.
Charge the battery fully before the test, and use the starter.
Charge a new battery also, they are not always fully charged, a low output charger is better, 6 amps or so, that automatically goes down as the battery charges. It may take several hours to charge.
The Cub service manual says a Cub engine before Cub serial number 192113 has 107 lbs of compression, when turning at 240 RPM. That is probably for a new engine.
Some less is ok, they have said on here 90 lbs or above is ok.
The piston rings may be stuck, and not wornout. It is common for them to get stuck when sitting.
They say on here if the engine is smoking, or the compression is low, if you can get it to run, to put Seafoam oil additive in the engine oil.
They sell it at auto parts stores.
It could help the compression, if the rings are stuck, and the Seafoam loosens them.
Make the engine work doing something when using the additive, so it warms up.
I have read on here of people having good results after using the oil additive.
It is easier to try the oil additive, than rebuild, or replace the engine.
One of the experts on here said to use the additive for 2 oil change periods.
The 1955 Cub operator's manual says to change the oil every 150 hours of use.
If the piston rings are wornout, the seafoam won't help much.
I have used Rislone, and had good results with that brand, it is an oil additive also.
I haven't used the Seafoam, but have read people's posts about it on here.
