Cummins/Onan — Carburetor Adjustment (Gasoline)
Adjustments
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Before you start
- Do not force needles into seats.
Procedure
- Turn adjusting needles in gently to seats. Do not force.
- Back main needle out about 2-1/2 turns.
- Back idle needle out about 3/4 turn.
- Start plant and warm up under full load.
- Slowly turn main needle inward until plant loses speed or voltage drops.
- Turn outward to point where plant carries full load.
- If hunting, turn out for richer mixture but not more than 1/2 turn beyond maximum output.
- Adjust idle needle warm with no AC load or lowest charge rate.
- Turn idle needle inward until plant loses speed, then outward until runs smoothly.
- Adjust throttle idle stop screw to clear throttle shaft stop by 1/32 inch at desired speed no load.
Tools required
- screwdriver Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- main 2-1/2 turns
- idle 3/4 turn
- throttle stop 1/32 inch
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.