Cummins/Onan 6.3 NHEL / 6.5 NH — Carburetor Mixture Screw Adjustments - Gasoline
Adjustments · Gasoline carburetor
For the Cummins/Onan 6.3 NHEL / 6.5 NH, from the Cummins/Onan service manual.
Applies to: Cummins/Onan NHEL
Before you start
- Forcing the mixture adjustment screws tight will damage the needle and seat; turn in only until light tension is felt.
Procedure
- Stop set and connect voltmeter, frequency meter, and load bank to generator output leads.
- Start set and apply full load; verify frequency within 59 ± 2 hertz, adjust governor speed nut if necessary.
- Turn main adjustment screw inward until voltage or frequency drops; locate highest point, then turn out an additional 1/4 turn.
- Remove load and verify frequency within 62 ± 1 hertz; adjust governor speed nut if necessary.
- Turn idle adjustment screw inward until voltage and frequency drop and engine runs rough or hunts; back out for smoothest operation.
- Pull governor linkage forward so throttle lever rests against throttle stop screw; adjust stop screw for 55 hertz and 100 (±4.5) volts.
- Release governor linkage, set voltage and frequency, adjust governor sensitivity.
- Add and remove a full load several times to make certain set does not bog down or hunt.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Preliminary: main screw out 2 ± 1/4 turns; idle screw out 1 ± 1/4 turn
- Full load frequency 59 ± 2 Hz; no load 62 ± 1 Hz
Full service-parts list: Cummins/Onan NHEL →
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.