hard starting f-20

[Alan in KY]

a friend of mine has a 1937 f-20 he just finished restoring and is having trouble getting it started when it is warm starts easy when it is cold. he thinks the timing is good and mag is hot what should he look for first to fix it alan

[RIRR]

Make shure that it is not boiling the gas out of the carb. When it is warm sometimes they will boil the gas out. And check the mag to make shure you have good spark(It will jump a 1/4" bright blue spark) If not it will start hard.

[Tony Thompson]

Hi Allen, Much of the time mags will get weak when they warm up due to a bad coil.

[tractorzippo]

Try adjusting valves according to marks on flywheel,just a sugestion!

[Robert Pence]

Make sure the mag coupling isn't tight. There should be some lengthwise clearance -- maybe .030 -- or the impulse might not trip properly. It could be fine when cold, but then tighten up because of expansion when the engine is hot. It would keep running OK, but if you shut it off and try to start it hot, the impulse coupling might not trip. Listen for the "CLACK" when cranking it. If it doesn't make that sound, you'll crank forever and run the risk of getting injured by kickback if you try to spin it.

The coil is probably the most likely suspect, but the coupling clearance can be checked visually/audibly without pulling the mag.