Just had my bike rebuilt and now it runs good up to about 30 minutes and then will just totally die on me. And will not start until it sits for about a half hour. Also while it is running there is a strong fuel smell coming from the exhaust and it is very black and wet. The bike guy replaced the choke flap in the carb with a new one without the flap thing hanging off it so could this have made any difference to it?? And after sitting for a half hour it will only run for a few minutes and then will die again, very fustrating. Any ideas??