Cummins/Onan — Adjust carburetor idle and load
Adjustments
From a Cummins/Onan service manual covering: 10MJC, 15MJC, 3MJA, 4MJA, 5MJB, 705MJB. Check it applies to your exact model before use.
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Procedure
- Run engine until warm.
- With no load, turn idle adjustment out until speed drops.
- Turn idle needle in until speed returns to normal.
- Apply full load.
- Turn main adjustment in until speed drops.
- Turn main needle out until speed returns to normal.
- Set throttle stop screw for 1/32 in. clearance.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 1/32 in. throttle stop clearance
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.