Generac GTV-760/990 V-Twin OHVI Engine

Tools: thickness gauge, spark tester

1. Rotate flywheel until magnet is under module (armature) laminations.
2. Place 0.008-0.012 inch (0.20-0.30 mm) thickness gauge between magnet and laminations.
3. Loosen mounting screws and let magnet pull magneto down against thickness gauge.
4. Tighten both mounting screws.
5. Remove thickness gauge by rotating flywheel.
6. Repeat procedure for the second magneto.
7. Repeat Test 29 and check for spark across spark tester gap.

Tools: feeler gauge, 10mm allen wrench, crow's foot

1. Adjust valve clearance with engine at room temperature.
2. Position piston at top dead center of compression stroke (both valves closed).
3. Loosen rocker arm jam nut; use 10mm allen wrench to turn pivot ball stud.
4. Check clearance between rocker arm and valve stem with feeler gauge.
5. Hold pivot ball stud; tighten rocker arm jam nut to 168 inch-pounds (19 Nm).
6. Recheck valve clearance after tightening jam nut.
7. Install rocker arm cover with new gasket; retain with four screws.

Tools: AC voltage/frequency meter

1. Connect AC voltage/frequency meter across Wires 11 and 44 at 50A main circuit breaker; verify 59-61 Hz.
2. Set Voltage Adjust pot fully counterclockwise; set Gain to midpoint (12 o'clock).
3. Set Stability and Under Frequency pots to midpoint (12 o'clock).
4. Start generator; perform this adjustment under a no-load condition.
5. Turn Voltage Adjust pot clockwise to obtain 238-242 VAC line-to-line.
6. If red regulator LED is flashing, slowly turn stability pot until flashing stops.

Tools: AC voltage/frequency meter

1. Perform adjustment with generator running at no-load.
2. Set AC frequency to 62 Hz (62 Hz equals 3720 rpm).
3. Adjust potentiometer to obtain about 252 volts line-to-line.

⚠ Do not rotate engine with electric starter with spark plugs removed

Tools: compression gauge

1. Remove both spark plugs.
2. Insert a compression gauge into either cylinder.
3. Crank the engine until there is no further increase in pressure.
4. Record the highest reading; repeat for the remaining cylinder.
5. Difference between cylinders should not exceed 25 percent.

Tools: Cylinder Leak Down Tester (Generac P/N 0F77000SRV), air source

1. Remove a spark plug.
2. Gain access to flywheel; remove the valve cover.
3. Rotate crankshaft until piston reaches top dead center (both valves closed).
4. Lock flywheel at top dead center.
5. Attach cylinder leak down tester adapter to spark plug hole.
6. Connect air source of at least 90 psi to leak down tester.
7. Adjust regulated pressure on gauge to 80 psi.
8. Read cylinder pressure; listen at carburetor, exhaust, crankcase breather.

⚠ If generator not producing AC, loss of governor control may cause overspeed; manually control throttle at 60 Hz / 3600 rpm

Tools: VOM, jumper lead

1. Unplug the six pin connector at the Voltage Regulator.
2. Disconnect Wire 14 from the Resistor (R1).
3. Connect jumper wire from removed end of Wire 14 to Wire 4 at Diode D1.
4. Measure and record AC voltage across Wires 2 and 6.
5. Measure and record AC voltage across Wires 11S and 44S.
6. Remove jumper; measure DC rotor amp draw between Wire 14 and Wire 4 at D1.
7. Shutdown; reconnect six pin connector and Wire 14 to R1.
8. Match results with the Test 4 Results chart.

⚠ Do not apply voltage longer than one second

Tools: Hi-Pot tester

1. Remove brush holder to completely isolate the rotor.
2. Attach all leads of all stator windings to ground.
3. Connect red tester lead to positive (+) slip ring nearest rotor bearing.
4. Connect black tester probe to clean frame ground on rotor shaft.
5. Set tester to 1500 volts; turn switch on and observe breakdown lamp.
6. Do not apply voltage longer than one second.
7. If breakdown lamp lights, clean and dry rotor, then repeat test.
8. If lamp lights on second test, replace rotor assembly.

Tools: Hi-Pot tester, paper clips

1. Insert paper clip into Pin 3 (Wire 55A); red probe to clip, black probe to Stator Lead 11.
2. Repeat with Pin 6 (Wire 2) and Pin 8 (Wire 55) against Stator Lead 11.
3. Using two paper clips, test Pin 3 (Wire 55A) to Pin 6 (Wire 2).
4. Test Pin 3 (Wire 55A) to Pin 8 (Wire 55).
5. Test Pin 6 (Wire 2) to Pin 8 (Wire 55).
6. Follow Hi-Pot steps 5a through 5c for each test.

⚠ Disconnect electronic components, relays, Voltage Regulators before high voltage insulation testing

Tools: Hi-Pot tester, paper clip

1. Disconnect stator output leads Wire 11 and Wire 44 from 50A circuit breaker.
2. Remove stator output lead Wire 22 from neutral terminal on back of 50A outlet.
3. Disconnect C1 connector from bottom of control panel (right side facing panel).
4. Connect terminal ends of Wires 11, 22, and 44 together.
5. Connect Hi-Pot red probe to joined leads; black lead to clean frame ground.
6. Set tester to 1500 volts; apply voltage no longer than 1 second.
7. If breakdown lamp lights, clean and dry stator then repeat test.
8. If stator fails second test, replace stator assembly.

Tools: external warm dry air source

1. Open generator main circuit breaker; apply no electrical loads while drying.
2. Blow warm, dry air through generator interior around rotor and stator windings.
3. Do not exceed 185 F (85 C).
4. Start generator and let it run for 2 or 3 hours.
5. Shut generator down and repeat stator and rotor insulation resistance tests.

⚠ Use proper safety precautions when handling gasoline

Tools: rubber mallet, flat blade screwdriver, 3 inch M12 x 1.75 bolt, 2x4 support

1. Disconnect and remove the battery from the generator.
2. Remove fuel tank; use proper safety precautions when handling gasoline.
3. Remove control panel; disconnect Wires 11, 44, 22 and C1/C2 connectors.
4. Remove air deflector from cross member; remove muffler and heat shield.
5. Disconnect Wire 4 and Wire 0 from brush assembly; remove brush assembly.
6. Remove four stator hold-down bolts; remove rear bearing carrier and stator can.
7. Remove rotor bolt; slot bolt and use 3 inch M12 x 1.75 bolt to break taper.
8. Remove four nuts from rubber engine mounts; remove engine. Reverse for assembly.