I have a fairly significant oil leak around the crankcase. When the engine is running there is a constant oil drip with a drip approximately every second. The engine is running really rough, popping and backfiring around the carb if I give it any throttle. Could the oil leak be contributing to the rough running condition? Would this cause a vacuum leak? This is a 2008 Big Bear 250 that I recently purchased. I have rebuilt the top end, adjusted the valves and torn apart and cleaned the carb. The air filter also looks to be in rough shape...

 

Hi,
- Oil leak should not contribute to rough running
- Oil leak will not cause a vacuum leak
- Check to ensure the intake boot is not cracked or loose
- Check valve clearance and timing
- Carb may still require cleaning, wire thru jets, as carb cleaner will rarely
clean the tiny holes and jets in the carb
Def replace the filter if its old...rotten or torn.