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Carter RBS Float Adjustment

As you see in the illustration, a float gauge is used to measure the float level. Carburetor kits no longer include this gauge, but have a measuring stick instead. Measure at the same points as in the illustration, but instead of the float gauge, use the measurement stick included in the carburetor kit, or other measurement instrument, such as a metal ruler.

The RBS carburetor used a black Nitrophy float and we recommend replacing this float each time you rebuild your carburetor. Nitrophyl floats tend to absorb fuel over time and without using a gram scale to measure the float, it is impossible to determine if the float is bad.


RBS Float Adjustment
Year/MakeFloat Level
1963-65 American Motors 195"15/32"
1965-67 American Motors 199", 232"15/32"
1968-69 American Motors 232"9/16"
1970-71 Ford 250"9/16"
1972-73 Ford 250" w/AC9/16"
1974 Ford 250"9/16"
1966-71 Kaiser Jeep 232"21/32"
1963-64 Studebaker 6 cyl15/32"
Kiekhaefer Mercury Marine MCM 80 4 cyl 89.7" Carb #: 4394S3/8"
OMC 120 4 cyl dual carbs Carb # 3971 & 420815/32"
OMC 150 V6 Carb # 395115/32"
OMC 155 V6 Carb # 420715/32"

Fast Idle Adjustment

Fast Idle
Fast Idle

Choke Pull-Down Adjustment

The choke pull-down is used to open the choke valve slightly when tromping on the gas and the choke is closed (cold engine).

Choke Pulldown

Bowl Vent Adjustment
Bowl Vent Adjustment is used to keep the float bowl vented. Not doing so will cause gas to be siphoned into the carburetor bore.
Hard starting when cold? Gas dripping into the bore? This may be the cause.

Bowl Vent

Accelerator Pump Adjustment


Adjust your accelerator pump. Out of adjustment can cause bogging when accelerating.
Pump Adjustment
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