Idle Mixture · Idle Speed · Fuel Pressure and Float Levels · Main Jet Adjustment · Maintenance
(NOTE: ALL ADJUSTMENTS PERFORMED ON FULLY WARMED UP ENGINE!)
Screw in and lightly seat, then back out 1-1/2 turns.
There are two adjustment screws, one primary(driver side, front throttle shaft), and secondary(passenger side, rear throttle shaft). Back primary screw all the way off, (not touching). With engine warmed up and running, adjust secondary screw to achieve within 100 to 200 RPM under desired idle speed.Adjust primary screw to desired idle speed (approx. 1/2 turn after contacting throttle lever).
Alky- 9 to 10 psi at wide open throttle under load.
Gas- 7 to 8 psi at wide open throttle under load.
If running belt drive style pump with low idle pressure (3 to 5 psi), you must raise pressure to about 6 to 7 psi to set float levels.For example, when checking primary float level, open secondary throttle plates to raise RPM and pump pressure, set primary level at bottom of sight plug hole. When setting secondary level, (at bottom of sight hole), open primary throttle plates to raise pressure.
Alky- center setting (position 3) is usually baseline.You have 2 adjustments richer (counterclockwise) and 2 adjustments leaner (clockwise). Each adjustment is a 4 jet change.
| Valve | Position | Jet | Valve | Position | Jet |
|---|---|---|---|---|---|
| A1 | 1 | 128 | A2 | 1 | 140 |
| 2 | 132 | 2 | 144 | ||
| 3 | 136 | 3 | 148 | ||
| 4 | 140 | 4 | 152 | ||
| 5 | 144 | 5 | 156 |
Gas- center setting (position 3) is usually baseline. You have 2 adjustments richer (counterclockwise) and 2 adjustments leaner (clockwise).Each adjustment is a 2 jet change.
| Valve | Position | Jet | Valve | Position | Jet | Valve | Position | Jet | Valve | Position | Jet |
|---|---|---|---|---|---|---|---|---|---|---|---|
| G3 | 1 | 60 | G4 | 1 | 70 | G5 | 1 | 80 | G6 | 1 | 90 |
| 2 | 62 | 2 | 72 | 2 | 82 | 2 | 92 | ||||
| 3 | 64 | 3 | 74 | 3 | 84 | 3 | 94 | ||||
| 4 | 66 | 4 | 76 | 4 | 86 | 4 | 96 | ||||
| 5 | 68 | 5 | 78 | 5 | 88 | 5 | 98 |
Alky- Weekly racing, lube throttle shafts with 3 in1oil or other light oil and grease pump cams. It's not necessary to drain fuel bowls, unless carburetor won't be ran for 2 to 3 weeks or more. If so, drain and refill with gas to break down alcohol. Alky carburetors need freshened yearly to avoid problems.
Gas- Weekly racing, lube throttle shafts with 3 in1oil or other light oil and grease pump cams.
To help keep black (powder coated) carburetors looking good, DO NOT USE CHEMICAL SPRAY CLEANERS (carb cleaner, brake cleaner, etc.) on coating. WD40 or similiar works well.
When bolting carburetor to manifold, don't tighten one corner down without others ran up snug, to avoid breaking baseplate.