5 or 6 years and it just woun't run aeh. Go to the phone order rebuild kits with brass viton tiped float neddeles. Before they come go to the auto parts store and score a can of carb cleaner. Pull the float bowls and the air filters and the air screws at a minimum. Take the little red tube that comes with the can and stick it in the hole were the air screw was. and blow. Watch were this comes out and the flow rate cause you need a pair of carbs they need to match. When you see it flowing well out the hole near the back of the throat, block it with your finger and make sure it's flowing out the tiny hole in the throat of the carb. Now replace the o-rings on all four adjusting screws there tight but don't use a tool that will cut them as you put them on. When your at the parts store get a small tin of o-ring grease too. The air screws are easy 1 1/2 turns off the seat to start. Now the slide adjustment screws need to go back were you found them so count the turns out and or take carful note of the size of the opening at the engine side of the slide so you can get back in the ballpark.Clean , clean and than clean again reassemble always thinking about a matched pair on all parts and adjustments. If you find little solid white nylon float neddles that was your problem most likley. Check float hieghts to speck sheets. If you really need it to run well you need to buy new neddles and neddle jets most likley. These are the highest wearing idem in any carb. norbsa