If the power valve in the carb is leaking, it will run real fat. Did you check the coil and condenser yet?

 

The coil and condenser are new & 12v. The coil has a built in resistor so one isn't needed externally. I guess I'd need to find spare coil/condenser to check them out.

 

See if the coil is hot when it quits running. Measure its resistance from (+) to (-) terminals when cold.

 

The float in the carburetor perhaps is malfunctioning.

 

Any chance the muffler is partly blocked & as it warms closes off? Fumes from a rich running engine have recognizable stronger smell; maybe someone more poetic can describe it better. Saw a question about ethanol in fuel, I've never had problems, nor do I use Stabil etc. This includes the F5 sitting in a barn for 2 yrs w/out running; cleaned the points, blew in the tank to push fuel up & it started.

 

I finally got the chance to spend a little bit of time on the truck today. (This is why I've been working on it for over 6 years!) I looked through the carb and everything looks really good. I measured the coil and it was 1.3 ohms. I bought the 12v conversion package from Vintage Auto Garage early in 2013. I was told the coil was 12V with the ballast resistor internal. I am thinking that I am reading just the primary coil and the resistor would add about 10 ohms to the coil. Could this be my issue?

 

1.3 is about what an external resistor coil for 12v would read. Does it say on the coil that it has an internal resistor? Most external ballast resistors are about 1.5 ohms. Easiest thing to do is throw a ballast in the wire to the coil from ignition switch and see if it helps.

 

I'm w/ Ross on the condenser . Went thru the same thing . Chasing a fuel issue when there was none . Condenser needs .021 - .025 micro farads . I now have a $600.00 condenser .

 

Wow Firstrider, that is quite a condenser! Well, the coil did not have the resistor in it. So I added the resistor (and changed the condenser to be safe) and it runs just fine now. Thanks all for your responses.

 

I think I'd carry a spare coil. Running without the ballast to the point it was not firing has likely done bad things to the insulation inside.