I am a Oliver 550 tractor owner, thinking of purchasing a local HG42.
The owner tells me it will fire right up and purr like a kitty but as soon as you put it under load it backfires, pops, and carrys on. He reckons a valve or magneto problem.
What does it sound like to you experts? Fuel line? Electrical? Or major work ahead? Many thanks in advance.
I'd first clean and set the points and check to see what the timing is set at.
Sounds like a timing issue. It could be set properly but a sloppy magneto drive would cause it to backfire when loaded.
Main jet may be plugged, or bad gas.
Best,
Mike
There is also a capacitor in the mag, if they go bad, they can cause your problem.