I can recall as a young lad riding with an elder brother in a borrowed IH KB-7, carrying a full load of timber. After a short time, the ole cornbinder decided she didn't want to go any more, when it came to full power.
She would start O.K., and run O.K., at moderate RPM, and light load .. but when it came to a hill with full power requirement, she would just cut right out and die.
My brother was a pretty skilled mechanic for his young age at the time, and I can recall he got pretty furious at the intermittent fault.
He eventually decided it must be a fuel supply block problem of some kind .. and he pulled off the fuel line from the tank to the first join, and rammed some wire through it.
Lo and behold, a chunk of sheet metal, in the shape of a disc, fell out on the ground! This little chunk of metal .. obviously a blank from a hole punched out on a die .. had been in that tank from new, we guessed .. but one day, it decided it would fit just the right way, to travel up the fuel line a little ways .. where it got jammed and acted as a butterfly valve.
The line was replaced, the ole cornbinder fired up, and went our merry way, with her producing full power on demand!
I've seen all manner of things that create weird fuel blocks .. and they ranged from blocked breather hole in the cap .. to all kinds of debris in the lines, rags, felt, globs of rust, foreign objects, tools .. rust pinholes in lines sucking in dirt and mud .. to filters plugged with muddy water.
If it was me, I'd be changing filters first .. then pulling off the lines and cleaning and checking them thoroughly .. and then also checking the tank thoroughly for accumulated crud, and foreign debris.
