I purchsed this bike brand new. It has sat for the last couple of years. Last time it ran it seemed to be only firing on 3 of the 4 cylinders. I have rebuilt the carbs with kits from the local dealer. The needle valves for the bowl floats had seazed. It will run if I feed it starter fluid to the air intake!! The fuel filter in the tank is clean as is the tank. any ideas?