Sounds like the nozzle is clogged or malfunctioning causing to much fuel to be burned thus giving off too much smoke. 1st thing is to pull off the top cover held down by 8 or so 5/16 bolts once removed you will see the nozzle you may be able to take it off and clean it. but i dont think there that expensive. Also maybe replace the fuel filter if applicable, you will see it inline before the nozzle. good luck