I mentioned in another post that my SC would cut out a bit sometimes idling and under a load...pulling my 2-12" moldboard plow. Another symptom was the SC exhaust was very sooty. It spat black specks all over the hood especially when I first cranked it. The Zenith up-draft carburetor has only one tuning screw. I monkeyed with that a bit with no success. I surmised that the timing was off and that it wasn't efficiently burning the fuel. The problem I had was that at some point in this tractor's lifetime, the TDC "pointer" had been removed. I could see the marks on the crankshaft fanbelt pully but there was no reference marker on the frame of the tractor. I was told that this "pionter" consisted of a bracket that was bolted to the front of the block near the hydraulic pump. I finally asked a retired IH mechanic to take a look at it. He noted that my distributor had some "play" in the shaft which was typical. In order to compensate for this, the previous owner had to open the points a good bit...in fact way outside what the service manual calls for. He also noted that inside the distributor, there was a good bit of metal shavings. He recommended that I replace the points first and see how well we could tune it. I should note that my SC has been converted from a 6V to a 12V system...and it does not have the magneto system. The distributor is purely stock (same as when it was a 6V). Here is a photo of the inside of the distributor with the shavings.
I'll update you on the outcome.
I'll update you on the outcome.