First time so hope I get things right. I have a 1987 Big Bear 350 4×4. It’s tan colored and the hi/lo/reverse shifter is on the left front fender. The throttle cable splits into two cables before the carb. Then it enters the carb at the top plate where it hooks to a flat slide and also into the side where it hooks to a butterfly. The carb is a Mikuni and the plastic plate on the side has "BTM" on it. It seems there is both a flat slide and a brass butterfly on this carb. My question is, What exactly do I have? It is very hard to keep running at starting but runs OK when it is warmed up. Do I need to reset the needle valve richer? It is set on the middle notch now. At first starting, I have to have fully choked and it will die until I restart fully choked about 5-6 times. Then it has to run fully choked for 3-4 minutes before I can take the choke off and use the 4-wheeler. If it is warmed up, it will start, but if it sits ten minutes or so its the same story. Colder weather makes the problem worse. Thank you in advance for any advise.