Cummins/Onan CW series Engine

⚠ Proper adjustment depends on correct governor adjustment.

Tools: voltmeter

1. Warm engine thoroughly before final adjustment.
2. Set idle needle with no load connected.
3. Set main needle with full electrical load applied.
4. Enrich until speed returns to normal.
5. Adjust float setting 1-1/4 in plus 1/8 minus zero.
6. Adjust throttle stop for 1/32 in clearance at rated no-load speed.

Tools: voltmeter, frequency meter

1. Warm up plant at light load.
2. Check 1/32 in throttle lever to stop pin clearance.
3. Disconnect booster external spring.
4. Turn speed adjusting nut for 60-61 cycles no load.
5. Apply full load; check cycle spread within 3 cycles.
6. Adjust sensitivity screw half turn if spread excessive.
7. Reconnect booster spring with no tension.
8. Verify frequency 1-2 cycles higher at full load.

Tools: hand crank

1. Remove magneto end cap.
2. Set breaker points to .020 in gap.
3. Remove right cylinder air cover to expose timing hole.
4. Slowly turn engine until IMP mark centers in hole.
5. Listen for magneto click at timing mark.
6. Loosen magneto screws and rotate to correct fast/slow.
7. Repeat until timing correct.

1. Remove magneto end cap.
2. Adjust breaker points to .015-inch gap.
3. Remove air cover from right hand cylinder.
4. Slowly turn engine until IMP mark centers in timing hole.
5. Listen for sharp click from magneto.
6. If click before mark, timing fast; if after, slow.
7. Loosen magneto mounting screws and turn magneto to advance or retard.
8. Repeat until proper timing attained.

Tools: 8 penny nail (1/8 in diameter)

1. Loosen carburetor choke arm on its shaft.
2. Slip choke assembly cover upward to remove.
3. Insert 1/8 in nail through aligning holes.
4. Tie armature firmly against core.
5. Set choke valve plate fully closed and tighten choke arm.
6. Remove nail, untie armature, replace cover.

1. Connect booster external spring to bracket on governor link.
2. With no load, slide bracket to position of no tension on external spring.
3. Apply full rated load; output voltage should stabilize.
4. If frequency rise more than 2 cycles, lessen internal spring tension.
5. If frequency dip, increase booster internal spring tension.
6. Clean small hole in short vacuum tube with fine wire.

⚠ Tappets too close may burn valves or score camshaft.

Tools: feelers gauge

1. Remove valve compartment covers.
2. Turn crankshaft one turn beyond valve closing point.
3. Check tappet on low point of cam lobe.
4. Adjust self-locking screws to 0.012 in cold.

Tools: test lamp set

1. For 120/240-volt single phase, contact test leads to the two collector rings nearest the ball bearing.
2. If the lamp fails to light, an open circuit in that winding is indicated.
3. Repeat contacting the two collector rings nearest the commutator.
4. If the test is made between the two middle rings, the lamp should not glow.
5. If it glows, a short between the two windings is indicated.

Tools: armature growler

1. An armature growler is required for this test.
2. Follow the test procedure recommended by the growler manufacturer.

Tools: test lamp set

1. Connect one test lamp lead to a bare metal point on the armature shaft.
2. Contact the other test lead to the commutator surface.
3. If the test lamp glows, the dc portion of the armature is grounded.
4. Repeat the test contacting the collector rings.
5. If the lamp glows, the ac portion of the armature is grounded.
6. Replace a grounded armature with a new one.

Tools: test lamp set

1. Connect one test lamp lead to a bare metal part of the generator frame.
2. Connect the other test lead to the coil terminal F+.
3. If the test lamp lights, a grounded circuit is indicated.
4. Remove the screws mounting one pole shoe to the frame.
5. Push the pole shoe and coil away from the frame.
6. If the ground is eliminated, the grounded coil is isolated.
7. Repeat until the grounded coil is located.
8. Repair the insulation at the point of damage.

Tools: continuity type test lamp set

1. Tag each lead wire and its connection point when disconnecting.
2. Connect one test lamp lead to the F+ coil terminals.
3. Connect the other test lamp lead to the F- coil lead.
4. If the lamp fails to light, an open circuit in the shunt winding is indicated.
5. Repeat the test between the S1 and F+ terminals.
6. If the lamp fails to light, an open circuit in the cranking winding is indicated.