When does it smoke, what colour is it and does it use a lot of oil or fuel. Blue smoke out the tail pipe is burning oil. (Rings). White smoke is water vapour ( damaged engine parts). And black smoke is excess fuel, ( Sticking choke or faulty fuel system parts). I suggest you take it to several mechanics and ask for a rough guess of the problem. If they all agree, that is probably your answer. Hope this helps.
derrick
June 2005