Cummins/Onan — Nikki Carburetor Main Mixture Screw Adjustment
Adjustments
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Procedure
- Carefully remove screw adjustment limiter cap.
- Turn main mixture screw inward until lightly seated.
- Back out exactly one and one-quarter (1-1/4) full turns.
- Replace limiter cap with limiter lever at LOW altitude position.
- Confirm limiter cap is fully seated over screw head.
Tools required
- Screwdriver Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Main mixture screw: 1-1/4 turns out
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.