Have had this tractor a ~35 years. Still original 6V + ground.
Started to have problems with misfiring followed by loss of spark when hot under load. I have replaced the ign switch and the resistor block with parts from here. Problem is still there. Fuel flow to carb drain is fine.
When it starts missing I if I jumper bat to coil side of resistor I can sometimes keep it running a while. I have also tried jumping directly to coil . About the same result. Battery is strong, turns motor over fine even when close to 0 oF. Proper voltage.
When cold the tractor starts up even in cold ( 10 oF) weather and runs fine, idles, has good power. Even when "warmed up" in winter problem seldom happens even when working hard moving snow. It's only when working it hard and it gets hot it starts to cut out. Did it today when plowing w/ a two bottom.
I have not been inside the distributor in a while but the way it runs cold, starts, and has good power makes me think points/timing is O.K. Plugs are new NGKs
I plan on pulling the distributor soon and have an old NOS CNH tune up kit I plan to install (good quality points, cap, rotor etc....). If that don't solve the problem I'm thinking the coil gets weak when it gets hot. Any other ides what could cause these symptoms?
Concerning coils, they seem to vary quite a bit in price, and I wonder about relative quality? The site here is ~$25, NAPA has Balkamp and Echlin, at ~$50 and ~$95 , respectively. Is the Echlin coil that much better to justify the price?
Thanks for suggestions/insight.
P.S. do you guys pull the genny so you can get at the distributor more easily?