RE: OS 91SII starting Problem
Sounds lean. But, without more details, its only a guess. You say "engine or tank have not been changed since last flight" I ask, "when was this last flight? July, Aug., Sept. The temps & conditions from those days are different then conditions here in December. The needles need to be richen'd (opened). If it was in December that your last flight was, then it still sounds lean, but might be dirt or something plugging, or blocking the fuel flow into the engine from the spray bar. You also say, "remove the fuel line & fuel flows through the line as it should" What is being done here? Fuel line just removed & nothing else, but fuel flows from the line? Is the vent line for the tank hooked to the muffler for pressure? Are you spinning the engine over with a starter & is that "when it flows as it should"? Just hand flipping it over? holding finger over exhaust ? Again, this sounds like it is lean, or not getting any, or proper fuel. Any & all things that can restrict fuel flow, or allow extra air, "vacuum leaks" will cause this kind of a condition, "runs on prime, & then stops". Check to make sure all gaskets & O-rings are in good shape & that all the bolts are tight. If all this looks good, just open the needle a turn & see how it reacts to that change.