Re: 1986 suzuki Dt 140
You might try a new set of spark plugs. They're cheap. While they are out see if any of them look different than the others. When you say its is missing, do you mean that it sounds like it is dropping a cylinder or does it just run rough? Since it seems to run pretty smoothly at mid range I would not think the ignition is the problem. You probably need to pull the carbs and do a thorough cleaning/rebuild on the carbs. Use carb cleaner AND compressed air, install rebuild kits, set the float height and idle air screw to manual specs.
