Hi there
I just purchased a 1993 Suzuki King Quad 300 4X4 and it was running good for about two weeks. Then I noticed it was starting to run a little rich due to the black smoke coming out the exhaust. It got to the point where it wouldn,t start for me one day. I pulled the plug and it was very black. I cleaned it up and got the quad up and running again. Now I'm at a point where the quad starts and idles fine. It also runs at half throttle fine, but when I open the throttle right up it bogs and alot of black smoke comes out the exhaust. It also does alot of backfiring. The carburetor does not have a butterfly or plunger choke. It has the fuel adding port choke. The carb does however have both a plunger and butterfly to control the throttle. Just wondering if anyone knows why the engine is getting so much extra fuel when the throttle is opened fully.

Thank You

 

Pull the carb and see what it might be.......