I am new to this forum and hope someone can help becuase I am at a loss for why my 1997 Suzuki King Quad 300 will not run properly. I've made numerous attempts to fix it and hope someone can give me some good advice before I need to take it and pay the dealer. Quad is new to me I purchased from original owner. Machine sat for many years and to get it running I needed to clean the carberutor twice. Once clean the machine ran mint for two different rides. Third ride machine started to bog out, sputter and skip. Sounded like it was running out of fuel and finally stalled. After getting it to restart a few times it sputtered and bogged but was able to drive me home. Replaced the fuel pump but haven't had any different results. Checked to see if fuel was flowing. Fuel flows out of petcock, into fuel pump and out of fuel pump when the motor is turned over. The quad can be riden and will start but doesn't like to idle especially when shifted into gear or back into neutral. Furthermore, if you do ride the machine and really get on it, it tends to clear up and will run normal for an unpredicatable amount of time. Then out of no where it starts to spudder and bog out or dies completely or if I get above 3/4 throttle in fourth or fifth gear it sputters and stalls out also. After giving it a few seconds of cranking, it normally will start again and run well enough to shift into gear and drive away. Sometimes driving away is spudders and bogs, other times it will take off as it should. I just cleaned the carb for a third time and triple checked that the fuel pump is working. The spark plug is black but not wet. Appears to be running rich and the air mixture screw is backed out 2.5 turns. I don't know if that is a serious enough issue to cause the symptoms listed above and I don't wanna mess with the mixture screw unless it really is my issue. Please help, there is no such thing as bad ideas I'll appreciate any advice!