i have a 77 cheetah with the 500cc twin spirit motor. and it runs, sorta. when it is running it lacks power, has no snap at all. when it gets warm it barley as enough to spin the belt. it did have old gas in it, put fresh in. didn't make much a difference. i think its a carb issue, but i haven't a clue with adjusting carbs. also the exhaust has a big hole were the header and expansion pipe come together. please help.