cup power loss

[macec3(TX)]

1951 cub - Starts quick but no power. As I release clutch the tractor stalls and dies. Sometime it will move but can't go up a slight incline. Would an improper point setting cause this? Thinking that a pertronix ignition might help. If not the point setting, what else could cause the cub to not have power?

[staninlowerAL]

Suggest a valve adjustment, tune up to include a compression test and you'll know more about the condition of the engine.

[Slim140]

Get a timing light and check the timing as well as what Stan suggested.

[gitractorman]

Cubs are pretty simple little engines, and extremely robust. I had one once, acting the same way. It had started and seemed to run perfect, but just no power. I started playing around with it and my dad came over with a pair of pliers and started pulling spark plug wires. We found out that it was only running on 3 cylinders, and in the process we had it running on 2 cylinders quite a bit. Surprisingly, it would sit there and run pretty darn good on 2 or 3 cylinders, enough that you wouldn't really notice it unless you paid close attention. Anyway, yours could be as simple as needing plugs and wires. However, as others have said, gunk in the valves, valves out of adjustment, and/or timing could all be issues too.

[Mike in Louisiana]

Also check that the governor is working correctly.

[Waif]

Cubs are pretty simple little engines, and extremely robust. I had one once, acting the same way. It had started and seemed to run perfect, but just no power. I started playing around with it and my dad came over with a pair of pliers and started pulling spark plug wires. We found out that it was only running on 3 cylinders, and in the process we had it running on 2 cylinders quite a bit. Surprisingly, it would sit there and run pretty darn good on 2 or 3 cylinders, enough that you wouldn't really notice it unless you paid close attention. Anyway, yours could be as simple as needing plugs and wires. However, as others have said, gunk in the valves, valves out of adjustment, and/or timing could all be issues too.

Hard starting in the cold and sluggish power like not running on all cylinders inspired changing spark plugs on mine. Did not hear the difference,but with the muffler off while cranking it only seemed to " pop" black smoke on about one cylinder. Just faint grey vapor on the others.
Gapped the new ones at .23 ( as they should be), switched them out and checked gaps on old ones. ....They averaged .35. Tractor performs much better.

[LRiddle]

Also check that the governor is working correctly.

I had a friend's Cub acting the same way, would start up and run nice but no power and it wouldn't take quick throttle changes. The only thing that changed from when it ran strong to when it was weak was I had the carb off to replace the manifold. Adjusted the linkage correctly and it ran strong again.

[macec3(TX)]

I think I solved the problem by accident. Yesterday pulled all the plug wires off to check the plugs. Cleaned all of the plugs and put them back in the head. When I reconnected the plug wires, got plenty of power. Didn't check the plug wires before taking them off so my thinking is that I had a couple of them on the wrong spark plug. Thanks for all the replies. Ya'll all have a good weekend.

[jsfarmall]

Good deal. That's always a possibility

[Indy4570]

woot, great!! always nice to have a easy fix.

[Slim140]

I put new plug wires on Walt a few years ago and mixed them up, it was running on 2 cylinders and had no power but it did run.