Rough runnin Cub?????????

[Jason (IL)]

I started to get my Cubs ready for winter tonight and the one miss fires pretty bad. So what I did is, started with new plugs, no help at all, then went on with a ne distributor cap and rotor, no help either, so I then changed all plug wires, which then again no help at all. I started thinking a little because the tractor ran perfectly two weeks ago, but we have had a lot of cool damp and soggy days so I though maybe there was a little bit of moisture inside of the disturbutor but no everything looks good. The Cub starts right up but misses like it is only hitting on three cylinders. My next guess is that maybe I have a stuck valve. The reason I say that is, I ran the tractor for a little bit and then checked all plugs and found the #2 plug to be the only damp plug and it wasn't as hot as the others too. But I started thinking again that maybe the condenser and points could be messed up a little but I don't know. I'm thinking of trying new points tomorrow night. Anybody have any thoughts on this one. I was thinking maybe an electrical short somewhere but have kinda rulled it out. I know for sure it isn't the carb because it is getting plenty of gas.
I am trying to get this one ready for plowing snow since it ran so good all summer and know have no idea what has gone wrong.

Thanks Jason

[Jim Becker]

Crank it over by hand, if compression feels about the same on all 4 cylinders, it probably isn't a stuck valve. Make sure you don't have a plug wire causing the problem. You might swap the #2 and #3 wires (BOTH ENDS) and see if the problem moves to the other cylinder.

[Clark Thompson]

I doubt you have a stuck valve but i think it could be 2 other problems causing your miss. It could be that a chunk of carbon has come loose from the cylinder head causing the valve not to seat. The next thing could be a worn vave and seat. The valve may have slightly turned casuing the worn seat not to seal. I any case you need to get a compression guage and do a proper compreaaion check.In 90% of the cubs i have rebuilt over the years the valve seats were worn bad. Also the valve face is grooved. Hope this helps!