Farmall 100 struggles to run when throttled up or gets too h

Hi, I have a Farmall 100 that has run great until recently. It idles and runs at below half throttle just fine, but when I up it over half it starts the stutter and quits if I don't throttle back. It also does it after being under working conditions after about 10 minutes. I had recently changed the distributor, wires, spark plugs, and coils. I'm thinking it might be vapor lock or something clogging up the jets or something in the fuel line. Any ideas?

I think you can rule out vapor lock but not a fuel issue...

Welcome tyler!

Could be fuel related, could be ignition...

A simple test would be a partial choke when it begins to quit. If there is improvement, even for a few seconds, that is a good indication there is a fuel problem.

What you describe could also be weak spark. If the partial choke has no effect, look at the spark quality at each plug. Best to catch it when it is giving problems, carefully pull each plug wire, one at a time off the plug. The spark should be able to jump 1/4" minimum. Recheck the point gap, try a different condenser. The new ignition parts are not the quality they used to be, common for them to be bad out of the box.

If the partial choke helped, look into the fuel system. Be sure the gas cap is vented. Check the screen above the sediment bowl, be sure it is clean and in place. While the bowl is off, open the fuel valve, see what kind of flow you get. Should be a good stream, not a drip. If there is an inline filter, that can be a source of a problem. They don't work well with gravity flow systems. The fuel line should be steel, not copper, routed as directly down to the carb as possible, no extra length, loops, kinks. Also needs to be away from the exhaust as far as practical.

On the bottom of the carb is a drain plug. With the fuel valve open, remove the plug and catch the flow in a clean glass. It should start as a full flow, slow to a trickle as the bowl empties, and continue to trickle. If it slows to a drip, or stops, there is a restriction or a problem with the needle/seat/float valve. Look at what is in the glass. If contaminated with water, rust, dirt, that will also be in the carb. The tank may need to be removed and dumped, rinsed out.

If you suspect the carb is contaminated, or needs attention, take it off, ease it apart. It is simple, probably won't need a kit if you are careful with the gasket. Clean every passage, set the float level, it will probably be OK.

Let us know...

Alright I'll get to it tommorow and let you know how it goes. Thanks for the help.

I had a 140 doing the same thing. Drove me crazy changing and checking parts with no improvement. Turns out it was the ignition switch... Had voltage to the coil even when it cut out. Easy to check by putting power directly to the coil with a jumper wire.