WICO C Magneto

1940 JD "B" engine stops after 90 minutes of work load. Carb has been rebuilt/restored and Mag is timed and set properly. "B" starts and runs like a champ for 60-90 minutes and then loses power and stops running. It's impossible to restart the hot engine until cooled for 2-3 hours and then restarts without problem. Saw on another thread the exact issue with an "H" and a new condenser solved this problem. So I installed a new condenser. Today after 90 minutes of operating a Woods mower, I got the "B" to the garage and then accidentally stalled the engine backing into garage. Do you think the "B" would restart? Back firing, popping, scaring the neighbors but no start. I saw on another thread to open the gap on a spare spark plug and checking the spark. I open plug to 1/8 inch but no plug spark. I remove the #2 cylinder plug and saw a large white spark followed quickly by 2 very small sparks all in the same one revolution of the flywheel. I was frustrated and didn't check #1 cylinder. Shame on me.

I guess my 3 choices are, points, cap, or coil. I'm taking a poll to see which of these might be the most popular to change next.

Think about what's causing your problem and U can make an educated guess. The heat is causing your problem. What does the heat affect? A crack in the cap if it has one. the coil maybe, I don't think the points but they're cheap. The trick is to think rationally and not panic. Might as well change the condenser too.

I bought a new tune up kit and put in mine and wasn't long it started dying. After checking everything I decided to put my old condencer back in it and that was my problem. You might start with a new condencer points rotor if that don't fix it I would get a new cap and coil. The cap and coil is what is going to cost you.

The same set of points and condenser and coil fires BOTH plugs, but if there are differences the bushing could be worn to where maybe the points gap isn't always the same due to wobble. As you already learned the classic causes of no fire after shes hot are condensors and coils and, of course, a hairline crack or carbon trace in the cap might act up once warm. If you already tried the condenser and it didnt help look at the cap under strong light and even magnification and the rotor also. If they look okay Id guess the coil as the next culprit ASSUMING POINTS ARE GOOD???? Try them first as they are cheaper then a coil. Id run a dollar bill between them just to remove any gray oxide build up. It don't take much oxide or burning or pitting or carbon on the points for them to give problems on a magneto.

John T