'41 9N Low Compression

[RobBruno]

I picked up a non-running 41 9N a while back and am getting around to hopefully getting it running again. The tractor has been very well maintained and the rubber and sheet metal are better then my 8N that I have used for years. The owner told me it was running the summer before, and when he went to start it after the winter, it would start. I was told it had no compression. I tested the compression and got the following results:

Cyl #1 Less the 30PSI
Cyl #2 Less the 30 PSI
Cyl #3 about 40 PSI
Cyl #4 about 60 PSI

I am hoping the rings are just dried and stuck so I want to start with some MM oil before anything else. I can look in the spark plug holes and see the valves are opening and closing. I cant see if they are seating properly, but I can see that they are not stuck open. I searched around but couldn't find the answer. I know a lot of people put the MM oil in, set for a couple days, rotate the motor, etc. But I am not sure how much people put in. So, how much oil do you guys recommend putting in each cylinder? Do you rotate the cylinders to close the valves before putting any in? I figure I would try this first before pulling the head or doing other major work. Also, have people used Sea Foam instead?
Thanks,
Rob

 

[Bruce (VA)]

We all have our personal 'snake oil' preferences. I like 50/50 ATF & diesel.

MMO or Seafoam are probably just as good, just more expensive.

Put a half cup or so in each cylinder, spin the engine over, then add another half cup. Let it sit a day or so. Then do it again.

After 2 tries and 2 days it should have done it's work.

But, with those numbers, you have more than stuck rings.
75 Tips

 

[R Geiger]

(quoted from post at 08:14:49 08/15/18) I picked up a non-running 41 9N a while back and am getting around to hopefully getting it running again. The tractor has been very well maintained and the rubber and sheet metal are better then my 8N that I have used for years. The owner told me it was running the summer before, and when he went to start it after the winter, it would start. I was told it had no compression. I tested the compression and got the following results:

Cyl #1 Less the 30PSI
Cyl #2 Less the 30 PSI
Cyl #3 about 40 PSI
Cyl #4 about 60 PSI


I am hoping the rings are just dried and stuck so I want to start with some MM oil before anything else. I can look in the spark plug holes and see the valves are opening and closing. I cant see if they are seating properly, but I can see that they are not stuck open. I searched around but couldn't find the answer. I know a lot of people put the MM oil in, set for a couple days, rotate the motor, etc. But I am not sure how much people put in. So, how much oil do you guys recommend putting in each cylinder? Do you rotate the cylinders to close the valves before putting any in? I figure I would try this first before pulling the head or doing other major work. Also, have people used Sea Foam instead?
Thanks,
Rob

Did you do both a dry and wet compression check?

 

[Bob]

Sometimes, when an engine sits a long time unused and someone tries to start it, old carbon deposits in the combustion chamber have flaked off and chunks can stick under the valves, preventing them from seating.

A compression test on an engine like this really has no bearing on the actual conditions of the valves and of ring seating.

If a "snake oil trick" brings up the compression a little and you can get it started, and RUN it and WORK it, and USE it, put some hours on it and then repeat the compression test.

Also, if you have a good helper, and can do it safely, a "pull start" can work wonders to get it started and running, getting the debris blown out of the cylinders and valves.

 

[RobBruno]

Bruce, that is what I am afraid of. When you say 1/2 cup, is that your ATF/Diesel mix or MM Oil?

For the compression test, I put the gauge on and cranked over several revolutions till the gauge went as high as it would go. Maybe 4 or 5 revolutions.

Agree that the valves might be sticking open. I have pulled the side valve cover off yet. Just started with what I figure might be the easiest fix to start.
Thanks

 

[RobBruno]

Meant to say I have not pulled the valve covers yet.

 

[Bruce (VA)]

" When you say 1/2 cup, is that your ATF/Diesel mix or MM Oil?"

I'd use a half cup each time of whatever you choose to use.

You can get an idea about the valves seating from the very first compression stroke; if it's say, 20 and max is 30, yea, the valves aren't seating.
75 Tips

 

[Tim PloughNman Daley]

You can use plain old charcoal lighter fluid if that is what you have around and no need to go out and buy the other stuff. It is 100% mineral spirits, and is the main ingredient in all the 'snake oil' products sold today. Mineral Spirits will not harm anything internally or externally except maybe your hands so wear gloves. Why do you think they all use it in their products? Nobody has any magical/secret formula. There is no "mystery" about it at all.


Tim *PloughNman* Daley(MI)

 

[Dean]

Before doing anything else, I would verify that the ignition is spot on and that carburetion is adequate for operation.

I would then pull start it and operate it for some time, monitoring symptoms, before performing proper dry and wet compression tests.

Dean

 

[RobBruno]

Just a quick update. I put some MM in each cylinder, turned it over a couple times, and let it sit. Couple days later, I actually lost compression on the two that had at least a little. How is that possible? Looks like I will be removing the head soon just to see what is going on. Anyone have any suggestions besides removing the head to check compression?
Thanks,
Rob

 

[L.Fure]

You may have sticky valve stems or tappets. Remove the side covers and spray carburetor cleaner, or some other product that will dissolve varnish deposits, on the valve stems and tappets. It won't work instantly so you will have to let it set for awhile, then add more cleaner. Spin the engine around, with spark plugs removed, while using the spray.

 

[RobBruno]

(quoted from post at 14:33:40 08/28/18)
You may have sticky valve stems or tappets. Remove the side covers and spray carburetor cleaner, or some other product that will dissolve varnish deposits, on the valve stems and tappets. It won't work instantly so you will have to let it set for awhile, then add more cleaner. Spin the engine around, with spark plugs removed, while using the spray.

I was thinking about removing the valve cover as well. I am just surprised it got worse. The valves are moving. I can see that through the spark plug hole. But, they could certainly not be seating correctly. I think I will do the cover before the head and see what I can find. I have another tractor so I am trying to avoid a complete rebuild if I can figure out what is causing the problem.
Thanks

 

[Hobo,NC]

More are less what bob is thinking... This one set up a year are so out side it had low compression on two cylinders. If I had put something like PB blaster in it and rotated the engine every now and again it may had dissolved the rust that was keeping the intake valve from sealing... None of the exhaust valves were seating good so I would have been headed in this direction anyways... In my opinion its a waist of time to remove the side cover poor you concoction right down the spark plug hole on top of the valves it has to go down hill into the guide... Worst case maybe it will help get the guides out if you go there...