we had a similar problem with the brother in laws triple and it turned out to be ice in the lines.we just let the sled sit inside for the night and she fired up the next morning without a problem.
I'm confused. You started this thread saying you have spark and fuel, but then you make the comment "No fuel enters the cylinder at any rpm." Which is it?
if u got compression, spark, fuel to the carbs but not entering the engine then simple carb problem. if fuel isnt entering the engine then its got nothn to do wit pipes, crank seals etc. it enters on 2 outta 3 cyl then its in the carb for that cyl.
It it doesn't start taking all the above advice into consideration, I would take a full 5gallon jerry can. Empty the gas can evenly on the exterior of the sled and throw a match to it, then resume drinking beer.
:d
there only two ideas come to mind float level and needle and seat is there
individual fuel pumps or just one air lock in fuel line due leaking seal on the line