ill start from the oldest time and work my way to present time. 1week ago my 450 would not idle (it sat for 8 months) i drained all the fluids and fuel and replaced it. i also changed the spark plug. it ran, but when ever i let off it backfires between 5-10 times. thinking it was due to a dirty carb i broke the whole carb apart and cleaned it all. still doing the same thing. i looked at the plug and saw that it seemed rich so i set the needle valve to 4 (leaner). all that did was make the engine chug and it still backfired. i reset the needle valve to 5.
my next thought was that it was the coil or timing but i was told by the dealer that he has never had to replace a coil or change the timing. i need advise! i am pretty much out of options