Join Date: Apr 2019
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01 AC ZR600 carb backfire
Chasing a backfire on the sled. I’ve replaced: plugs (eya) plug caps, reeds (Boyesen), reed cage gaskets, in-tank screener and fuel line, tank to fuel pump fuel line, fuel pump to carb line, fuel filter.
I’ve cleaned the carbs 4xs, looks like one float was recently replaced, other original.
Adjusted fuel mixture screw 1.5 turns out.
Drained tank and filled over half tank with new fuel.
I’ve checked exhaust pipe and can for obstruction, no tears in carb boots or intake rubber.
I DID clean a nest out of the silencer box. Cleaned that as well as the tray the silencer box sits on top of.
Tested conduincy of stator and ground. Scrubbed and sprayed grounds with elec cleaner.
Compression test (110 both).
Prob done more but have done a lot. Sled starts on one pull and idles but it backfires (poofs) at carb exit (I can see smoke come from the manifold to exhaust pipe connection).
Stator ohms-out fine but still may be issue. Maybe it’s crank seals? Maybe it’s key way stuff?
The only thing I can think of is replacing the old float or tuning the problem out with mixture screw? Throw a coil pack at it?
Any ideas appreciated, thanks