[Farmall] Spark plugs and Cubs.

[Dan Glass]

It happened once again, a friend of mine came over for a visit and he 
told me he was going to have to overhaul his cub. I ask what it was 
doing and he said it didn't have enough power to even pull itself in 
first gear.  I told him that before I would overhaul it, I would check 
to be sure it didn't have AC spark plugs in it.  Put a set of Champion 
D21's in it first.  He assured me that that wasn't the problem and I 
said lets do it anyway. So we went to his house and he cranked it up and 
it idles just fine, but once it goes in first and the clutch is let out 
it dies.  We pulled the plugs and sure enough they were AC.  They look 
fine and I don't understand why this happens, but we put in the 
Champion's and he cranks it up.  I tell him to put it in third gear, 
leave it at idle and let out the clutch.  And away he goes with no 
problems.  He said he wouldn' t have believed it if we hadn't have tried 
it.  I have seen this happen on several of other occasions.  Are 
Champion's the only plug designed for these old tractors?  When you put 
a new set of AC's in they work fine for a couple of hours and then the 
power tales off to nothing and it won't regain it. Is this just another 
Cub mystery?