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naa loses power

don 53 NAA starts easily & runs fine at about 30psi oil pressure for about 10 minutes. After about 10 minutes the oil pressure starts to drop and the tractor loses power. When I turn off the ignition it chatters until stopping. Using 40w oil, rod bearings were replaced and torqued to specs at last oil change. However a snap ring was found in the bottom of the pan-any idea if this is from the governor or ? and where to look. Always chatters when shutting down but always starts and runs fine for 10 minutes.
Bob G Have you checked for fuel flow out the botom of the carb? should fill a pint jar in 2 to 3 minutes,
If it trys to continue to run when you turn the key off you may have carbon build up in cylinders. burning carbon will act like a spark plug and fire the mixture.

I would be pretty nervous about the snap ring. I am not familiar with that engine but I think I would be taking a real close look at a parts manual for the engine.

mark sr I don't know about the snap ring either but I'd sure want to find out where it came from!

Timing being off can also cause it to run on after shut down. Higher octane can sometimes counteract carbon build up in cars ..... never had that issue with my NAA.

Jim Loveridge The snap ring might a piston pin retainer. The worse that could happen is the pin could slide over enough to score the cylinder, but it can't come all the way out. What does the oil pressure drop to? The loss of power might be a weak spark because the coil is breaking down. Check to see if it's getting hot when you lose power.
don Thanks for the thoughts. Oil pressure drops to about 5 psi. Would the coil affect the oil pressure? If I let it sit for about 15 min. the pressure will be back up but then the problem reoccurs. The engine doesn't continue to run when I turn it off but it does make a clatter as it shuts down. No noticeable clatter at higher speeds though and seems to run fine. Appreciate the responses.
Bob G If you are losing RPMs then the oil pressure will drop. So you are saying the clattering sounds is durning coast down not as in the engine tries to keep running.
Jim Loveridge The coil would have nothing to do with oil pressure. 5 psi is pretty darn low. You might do a compression check, but from what you are saying, it sounds like your engine is just plane tired. It might be time for an overhaul. You have a good start with new rod bearings.
don Well took the Jubilee out for a drive Sunday to give an update on how it sounds and acts. Started right up and made it a half-mile down the road before it quit running. A neighbor ended up towing me back to the garage. Turns out the fuel filter was plugged so I will try it again when I get it replaced. Oh well, 4 neighbors I don't get to see often stopped and talked tractors for a half-hour so it was good. Will be back here for more advice later. Thanks everyone
Bob G so did you check for fuel flow like I suggested? Doesn't sound like it!

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