Cummins/Onan NH-MS/1 / NH-S/1 — Carburetor Adjustment (Idle and Main Fuel)
Adjustments
For the Cummins/Onan NH-MS/1 / NH-S/1, from the Cummins/Onan service manual.
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Before you start
- Do not force the needle valves against their seats; this will bend the needle.
Procedure
- With no load, turn the idle adjustment out until engine speed drops slightly below normal.
- Turn the idle needle in until engine speed returns to normal.
- Apply a full load to the engine.
- Carefully turn the main adjustment in until speed drops slightly below normal.
- Turn the needle out until speed returns to normal.
- Set the throttle stop screw to allow 1/32 inch clearance to the stop pin at no load.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- If completely out of adjustment, open both needle valves 1 to 1-1/2 turns off their seats to permit starting
- Throttle stop clearance 1/32 inch at no load
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.