Hi all - just acquired a new to me Ventrac 4100 (old I know but in great shape for a ~20 yo machine). It hasn't wanted to start now that it's cold out (it has a carb'd/air cooled 25hp Kawasaki FH721d) but now is the fact that it bogs down to 1200-1500 rpm, puffs black smoke, and stalls out with...