I am working on a 250 atv 4x4 1993. It is hard to start but when it does it seems to run okay for about a half hour, medium to full throttle then dies. You then can hear fuel boiling in the carb. And it will not start until it cools off. The other problem is the choke, what is the procedure to adjust it,the previous owner drilled the plug out where the choke plunger fitting threads into and put in a bolt you can remove the bolt and see the choke plunger.