i have a 95 300ex it will only run if the throttle is wide open but then it wont get to its highest rev. and its sputtering the whole time. i cleaned the carb. all the jets are clean its got good gas new spark plug and its getting plenty of gas and when i let off the throttle it cuts off and black smoke blows out the exhaust and the carb. sometimes anyone got any ideas of what it could be?

 

Is the air filter caked with gunk, and is the float working properly? Is the enricher/choke working correctly?

Unless the smoke is actually bluish and smells of oil, I think you are either getting no air or way too much fuel.

 

the air filter is new and the enricher/choke is working right but in not sure about the float. if i have the throttle wide open the carb shots a mist of gas out of the intake constantly. and it wont run with the choke on

 

Check the jet needle on the carb slide.