Complaint:
Lean at high speed (part to wide open throttle) in Carter W1, WA-1, WO, WDO 1-barrel carbs
Possible cause:
Low fuel pump pressure
Restriction in gas line connection to needle seat. This does not allow sufficent gasoline to enter bowl for high speed driving
Low float level
Opening in needle seat too small (the wrong needle and seat)
Restricted outside vent hole
Restriction between metering rod and jet
Improper metering rod setting or parts that operate metering rod worn. (bowl cover, pump arm, throttle rod, throttle shaft arm)
Wrong metering rod (too large in diameter) or wrong metering jet (hole too small)
Restriction in casting from metering rod jet to nozzle
Damaged nozzle
Screw nozzle fails to seat in slip nozzle (air bleed nozzle)
Two nozzle gaskets installed on nozzles that should have only one nozzle gasket. A nozzle that has a tapered seat where it seats in the casting does not require a nozzle gasket (early W-1 carburetors). If the nozzle has a flat seat, it takes a nozzle gasket
Air horn assembly loose on casting
Worn throttle shaft
The anti-percolator should be closed air tight when fuel is discharged out of nozzle. That’s why it is very important to set anti-percolator properly so that it is opened at idle speed or closed throttle and closed just before fuel is discharged from nozzle.
Complaint:
Lean on acceleration
Possible causes:
Weak plunger spring.
Worn or dried out plunger leather or weak pump spring.
Leather loose, not installed tight on plunger
Damaged or cracked plunger leather
Wrong plunger assembly
Intake or discharge check not seated in casting
Leaking or sticking intake or discharge check
Passages in casting for pump restricted
Pump jets restricted or not seated in casting
Pump disc check sticking or leaking
Pump not adjusted properly
Wrong parts
If linkage from throttle to accelerating pump is worn, the mixture will be lean. When throttle is moved open from closed position, the pump jet should start to discharge instantly. Therefore, there should be little play in these parts.