Cummins/Onan 6.5 NH Generator Set

1. With set stopped, turn lever counterclockwise; set screw so plates are closed but not binding.
2. Check lever has approximately 30 degrees travel counterclockwise from vertical.
3. Start set; lever should rotate approximately 60 degrees clockwise from stopped position.
4. Check solenoid plunger is fully seated.
5. If not, adjust distance between plunger and lever arm; repeat steps.

⚠ Ignition adjustments should be made with the engine in a static condition and cold.

⚠ Make sure feeler gauge is clean and free of any grease, oil or dirt.

Tools: Allen head wrench, Flat thickness gauge (feeler gauge), Hex-head socket and socket wrench

1. Disconnect negative (-) battery cable at battery terminal.
2. Remove breaker box cover clip and lift off cover.
3. Remove spark plugs; turn rotor through-bolt clockwise until breaker point gap is open maximum.
4. Remove condenser mounting screw and disconnect condenser and ignition leads; lift out condenser.
5. Remove breaker points mounting screws and lift out point assembly.
6. Replace condenser and point assembly in reverse order of removal.
7. Use allen head wrench to adjust set screw to obtain the gap setting specified in Section 2 Specifications.
8. Measure point gap with a flat thickness gauge; clean points after adjusting.
9. Timing is set during initial engine assembly and fixed by point gap adjustment; no other adjustment necessary.
10. Replace point box cover, spark plugs, and spark plug leads.
11. Connect negative (-) battery cable to negative battery terminal.

⚠ Make ignition adjustments with the engine stopped and cold. Make sure feeler gauge is clean and free of grease, oil or dirt.

Tools: Feeler gauge / flat thickness gauge, Allen head wrench

1. Remove cover by loosening screw and lift off.
2. Turn the engine crankshaft (with rotation) until the maximum breaker point gap is obtained.
3. Using an allen head wrench, adjust set screw for 0.020 inch (0.51 mm); measure gap with a flat thickness gauge.
4. Replace point box cover.

⚠ Forcing the mixture adjustment screws tight will damage the needle and seat; turn in only until light tension is felt.

Tools: Voltmeter, Frequency meter, Load bank, Screwdriver

1. Stop set and connect voltmeter, frequency meter, and load bank to generator output leads.
2. Start set and apply full load; verify frequency within 59 ± 2 hertz, adjust governor speed nut if necessary.
3. Turn main adjustment screw inward until voltage or frequency drops; locate highest point, then turn out an additional 1/4 turn.
4. Remove load and verify frequency within 62 ± 1 hertz; adjust governor speed nut if necessary.
5. Turn idle adjustment screw inward until voltage and frequency drop and engine runs rough or hunts; back out for smoothest operation.
6. Pull governor linkage forward so throttle lever rests against throttle stop screw; adjust stop screw for 55 hertz and 100 (±4.5) volts.
7. Release governor linkage, set voltage and frequency, adjust governor sensitivity.
8. Add and remove a full load several times to make certain set does not bog down or hunt.

⚠ Forcing the mixture adjustment screws tight will damage the needle and seat; turn in only until tension is felt.

Tools: Voltmeter, Frequency meter, Load bank, Screwdriver

1. Turn mixture screws in until lightly seated for preliminary adjustment.
2. Turn main adjustment screw out 2-1/2 (±1/4) turns and idle adjustment screw out 1 (±1/4) turn.
3. Start engine and run about 10 minutes at light load.
4. Connect voltmeter, frequency meter, and load bank; start set and apply full load; verify frequency within 59 ± 2 hertz.
5. Turn main adjustment screw inward until voltage/frequency drop, then outward until they drop again; set at highest point.
6. Remove load and verify frequency within 62 ± 1 hertz; adjust governor speed nut if necessary.
7. Turn idle adjustment screw inward until voltage/frequency drop and engine runs rough; back out until engine runs smoothly without hunting.
8. Pull governor linkage forward so throttle lever rests against throttle stop screw; adjust stop screw for 55 hertz and 100 (±4.5) volts.
9. Release linkage, set voltage and frequency, adjust governor sensitivity; add and remove half load several times.

1. Turn idle mixture screw out 3/4 to 1 turn from seated.
2. Turn main mixture screw 1-1/2 to 1-3/4 turns out from seated.
3. Start set; adjust governor spring for 1860 RPM no load (62 Hz or 130 volts).
4. Hold governor arm so throttle lever rests on stop; adjust idle stop screw to 1500 RPM (50 Hz or 100 volts); release.
5. Adjust idle mixture screw to highest RPM or voltage; readjust governor spring to 1860 RPM no load.
6. Apply full load; adjust main mixture screw to highest RPM or voltage; readjust governor spring to 1770 RPM full load.
7. Remove and add load several times to check hunting; readjust governor spring if required.

⚠ The choke gets very hot during normal operation and can cause severe burns if touched. Do not remove choke cover while the set is operating.

Tools: Screwdriver

1. Stop set and allow it to cool down before making adjustments.
2. Remove protective plastic choke cover and loosen heating element cover screws.
3. Rotate heating element until choke plate is about halfway open.
4. Slowly rotate cover counterclockwise while tapping the carburetor choke lever until it no longer bounces (fully-closed reference position).
5. Refer to Table 6-3 for degrees to rotate element cover clockwise from reference position (marks spaced at 5 degrees).
6. Rotate element cover as specified and tighten cover mounting screws.
7. Move choke lever back and forth to check smooth operation and automatic return.
8. Install plastic choke cover and tighten center mounting nut.

⚠ The choke cover gets very hot during normal operation and can cause serious burns if touched. Do not touch the choke cover while the set is operating.

1. Loosen the two mounting screws and rotate the choke cover until the correct setting is attained.
2. Check the setting by starting the engine and observing its operation.
3. Retighten the mounting screws after adjustment.

Tools: Vacuum source (4 to 18 inches Hg), Measuring gauge

1. Remove the complete air filter assembly to provide access to the choke plate.
2. Disconnect diaphragm hose from intake manifold and apply 4 to 18 inches (102 to 457 mm) Hg vacuum to the diaphragm.
3. Apply light finger pressure against the choke lever to take up all freeplay in the pull-off linkage.
4. Check alignment of diaphragm stem, pull-off linkage, and slot in choke lever; correct as required.
5. Measure distance between choke plate and bottom of carburetor; bend diaphragm mounting bracket to obtain 0.39 to 0.43 inches (9.9 to 10.9 mm) clearance.
6. Move choke lever back and forth to check for free movement; verify choke does not bind or stick.
7. Remove vacuum supply from diaphragm and install filter assembly on carburetor.

⚠ Touching hot exhaust pipes or moving parts might result in serious personal injury. Use extreme caution when making adjustments while the engine is running.

Tools: Voltmeter, Frequency meter

1. Run the unit about 10 minutes under light load to reach normal operating temperature.
2. Adjust the carburetor idle and main adjustment screws as specified in the Mixture Screw Adjustments section.
3. Adjust the length of the governor linkage and check for binding or excessive looseness; adjust ball joint so the throttle shaft stop almost touches the carburetor stop.
4. With the warmed-up unit at no load, adjust governor spring tension to obtain 127 volts and 61 hertz.
5. Check voltage and speed with load and without load; adjust sensitivity for closest regulation without hunting.
6. Recheck the speed adjustment, then set the carburetor throttle stop screw.

⚠ Forcing the mixture adjustment screws tight will damage the needle and seat; turn in only until light tension can be felt.

⚠ T-handled main adjustment screws are locked by a packing nut; loosen before adjusting and retighten afterward. Failure to tighten the packing nut might result in leaking fuel, creating a serious fuel hazard.

Tools: Voltmeter, Frequency meter

1. Remove all electrical loads and connect a voltmeter and frequency meter to the generator set.
2. Pull the governor linkage toward the front of the set so the throttle lever rests against the throttle stop screw; adjust the stop screw for 90 to 100 volts.
3. While holding the governor linkage, turn the idle adjustment screw inward until voltage drops, then outward until it drops again; set slightly rich from the midpoint.
4. Release the governor and apply full load; set the main adjustment screw the same way, slightly rich from the midpoint.
5. Remove the load and check stability; adjust governor sensitivity; add and remove full load several times to be sure the set does not bog down or hunt.

⚠ Adjust the valve clearance only when engine is at ambient temperature.

Tools: Socket wrench, Feeler gauge

1. Remove all parts necessary to gain access to valve tappets.
2. Remove spark plugs to make turning the engine easier.
3. Rotate crankshaft clockwise until left intake valve opens and closes; continue until TC mark on flywheel lines up with TC mark on gear cover (left piston #1 at top of compression stroke).
4. Verify left intake and exhaust valves are closed and there is no pressure on valve lifters.
5. For each valve, the gauge should just pass between the valve stem and valve tappet.
6. Turn the self-locking adjusting screw as needed to obtain the right clearance.
7. To adjust right cylinder valves, turn engine one complete revolution and realign the marks, then repeat.
8. Replace all parts removed; tighten all screws securely and torque manifold bolts.