How can this be?

[OLDIRON]

So I picked up this 1972 Yachtwin. I have no idea how long it's been sitting. I put fuel to it and it started up. Seemed to run OK. Now before I want to go any farther, I took the flywheel off and checked the points and any damage to the mags. They are in great shape except the bottom cyl. mag points were not set at .20. It barely opened, maybe .10. Bottom plug was fouled pretty bad. Today I took a compression test. 60 in the top cyl. and absolutely nothing, and I mean nothing on the bottom. Would not even hold any pressure. So I figured the bottom cyl. is shot, may have a hole in the piston, but I start it up and it ran anyway. The more I ran it, the better the motor runs. It now idles down, and runs perfectly at full throttle. Doesn't miss a beat. Runs very smooth. Took another compression test. 80 in the top and now 60 in the bottom. What do you think? Is the head gasket bad? Are the rings in the bottom stuck? The more I run it the better it gets. This does not make any sense to me. Usually once a cyl. is dead, it's dead.

 

[Grub54891]

The rings were stuck. Now they are freeing up. You could do a de-carbon on the motor and get it cleaned up. Or just run it for awhile longer and see what she does. Best to change the gear oil, and impeller before running it anymore though.

 

[Bosunsmate]

Some folk tip the motor up and pour atf fluid in the cylinders to help free up the rings, you can do one at a time making sure it doesnt pour through the exhaust/inlet ports

 

[Bosunsmate]

Changing the head gasket and cleaning out the water channels is good maintenance, preventive maintenance, so long as the bolts back out ok

 

[Joe Reeves]

Sometimes...... Ya'jest git flinged a goodie! Suggest you buy a lottery ticket quickly!

 

[OLDIRON]

The rings were stuck. Now they are freeing up. You could do a de-carbon on the motor and get it cleaned up. Or just run it for awhile longer and see what she does. Best to change the gear oil, and impeller before running it anymore though.

Thank you. Yes I do believe that is the problem. I worked on it today, and ran Seafoam with the fuel. The compression is slowly but surely coming up on that cyl The more I ran it the better it got. Pulled #1 plug wire while it was running and it still ran, not great, but it ran. Pulled #2 and it also ran. Not great, but it ran. My guess is that # 2 was not running for a very long time because the points were not opening for that cyl. This motor appears to have very few hours on it so I couldn't imagine the rings were wore out. Eventually maybe I will pull the head and clean up the top of both cylinders , but for now I will let sleeping dogs lie. I don't need a broken head bolt if I don't have to.