Float Level Too High
If the float is set too high or if it's sticking, it can cause the fuel bowl to overflow, sending too much fuel into the engine. Set the float at specifications. Look closely at the float pin for any wear.
Float Too Heavy
Nitrophyl floats can absorb fuel over time. Weigh the float for 8 grams.
- Worn or Leaking Needle and Seat
- If the needle valve or seat is worn, it might not shut off fuel flow properly, leading to flooding. Dirt may be getting into the seat via a dirty gas system. Even a fuel filter can't keep it all out. If pressure was put on the needle while adjusting the float then it will surely leak. Inspect for ridges.
Choke Sticking Closed
If the choke doesn't fully open after warm-up, it will keep enriching the mixture like the engine is cold.
Vacuum Leaks (Rare for Rich, but possible in strange ways)
Normally vacuum leaks cause a lean mixture, but if the leak is on a choke pull-off line or a vacuum diaphragm controlling the choke, it can cause the choke to stay closed too long.
Power Valve (or equivalent enrichment system)
If the enrichment circuits are malfunctioning or even a weak power piston spring, it can cause over-fueling.
Fuel Pressure Too High
If you have an aftermarket or malfunctioning fuel pump delivering too much pressure, it can overpower the needle and seat and flood the carb. Test the pump for about 4.5 lbs. New pumps are especially suspicious.
Dirty Air Filter
If the air filter is clogged, not enough air gets in, making it run rich.
Quick checks you can do:
Pop off the air cleaner after warmup — is the choke fully open?
Smell of fuel strong at idle?
Black smoke from the tailpipe?
Pull a spark plug — is it black and sooty?
