Brian: I had a chipper shredder that would run perfectly for quite some time...like an hour...then suddenly spool down and quit for no reason. I'd walk over and pull the starter and it fired right back up, ran for another hour, then quit again. Nobody ever figured out why but two explanations kept coming back:
1. The coil would "swell" with heat and somehow lose it's ability to export juice; something to do with the laminations of goop and paper inside the coil. (I'm skeptical..but the price of a coil is cheap. I also don't understand coils.)
2. The float bowl would slowly drain because a restriction in the little shut-off valve in the fuel line would not allow enough fuel into the bowl under periods of load. The few seconds it would take me to walk over and pull the cord was enough to refill the bowl. Then, after a while, it would drain again depending on load.
I believe #2 was the reason...but, then again, the engine would not falter and stumble, it would QUIT. That had more of an electrical profile to my thinking.
#3 could be that it was haunted or just lazy.