Generac Generac OHVI Engine

Tools: allen wrench, feeler gauge, crows foot

1. Engine must be at room temperature with piston at TDC of compression stroke.
2. Loosen the rocker arm jam nut.
3. Turn the pivot ball stud with an allen wrench while checking clearance with a feeler gauge.
4. Correct clearance is 0.001-0.003 inch (0.03-0.07 mm).
5. Hold the pivot ball stud and tighten the rocker arm jam nut to 65-85 inch-pounds.
6. After tightening the jam nut, recheck valve clearance.

Tools: pliers

1. Loosen the governor clamp bolt.
2. Push spring end of governor lever clockwise to wide open throttle position of lever.
3. Hold lever at wide open throttle; rotate governor shaft fully clockwise with pliers using minimum force.
4. While holding shaft fully clockwise and lever at wide open throttle, tighten governor clamp bolt to 70 inch-pounds (8 N-m).
5. Start engine, let it stabilize and warm up at no-load.
6. Turn the adjuster nut to obtain a frequency reading of 62 Hertz.
7. If droop is excessive, move the governor spring down one slot on lever; for greater stability move it up one slot.
8. Recheck frequency and readjust adjuster nut to obtain 62 Hertz at no-load.
9. Check AC voltage reading; if incorrect the voltage regulator may require adjustment.

Tools: feeler gauge, 8mm allen wrench, crow's foot torque wrench

1. Adjust valve clearance with engine at room temperature, piston at TDC of compression stroke (both valves closed)
2. Alternatively, position intake valve fully open to adjust exhaust valve, and exhaust valve fully open to adjust intake valve
3. Loosen rocker arm jam nut; turn pivot ball stud with 8mm allen wrench while checking clearance with feeler gauge
4. Tighten rocker arm jam nut to specified torque with crow's foot while holding pivot ball stud
5. Recheck valve clearance after tightening to ensure it did not change
6. Install new rocker arm cover gasket and reinstall cover with four screws; install oil breather tube

Tools: voltmeter

1. Set frequency to 62.5 Hertz with no load on the generator
2. Slowly turn the voltage adjust pot on the voltage regulator until 124 VAC is measured

⚠ Adjustment of the voltage adjust potentiometer must be done only when the unit is running at its correct governed no-load speed.

1. Run unit at correct governed no-load speed; no-load AC output frequency should be about 62.5 Hertz.
2. With no load on the generator, slowly turn the voltage adjust pot on the voltage regulator until 124 VAC is measured.
3. If voltage is not adjustable, proceed to Troubleshooting Problem 2.

Tools: screwdriver

1. Place the flywheel on a wooden surface.
2. Hold a screwdriver at the extreme end of its handle with its point down.
3. Move the tip of the screwdriver to about 3/4 inch (19mm) from the magnet; the screwdriver blade should be pulled in against the magnet.

⚠ Do not apply voltage longer than 1 second.

Tools: megohmmeter / hi-pot tester

1. Disconnect wires from the Rotor brushes or remove the brush holder with brushes.
2. Connect tester positive (+) lead to positive (+) slip ring (nearest the Rotor bearing).
3. Connect tester negative (-) lead to a clean frame ground (such as the Rotor shaft).
4. Apply 1000 volts. Do NOT apply voltage longer than 1 second.
5. If breakdown is indicated, clean and dry the Rotor and repeat; replace Rotor if it fails the second test.

Tools: digital multimeter (VOM), tachometer capable of reading up to 1,500 rpm, fully charged 12-volt battery

1. Set the meter to read DC amps.
2. Connect the starter motor, battery and VOM as shown.
3. Insert the tachometer at end of the pinion gear and activate the starter motor.
4. A starter motor in good condition will meet the specifications; if not, replace it.

⚠ Insulation resistance testers such as hi-pot testers and megohmmeters are a source of high and dangerous electrical voltage.

⚠ Do not connect tester leads to any leads routed into the generator control panel.

Tools: Hi-pot tester or megohmmeter

1. Disconnect and isolate all Stator leads (11S, 22S, 11P, 22P, 33, 44, 2, 6, 55, 66, 77).
2. Connect the terminal ends of all Stator leads together.
3. Connect tester leads across all Stator leads and to frame ground on the Stator can.
4. Apply a voltage of 1500 volts. Do NOT apply voltage longer than one (1) second.
5. If insulation breakdown is indicated, clean and dry the Stator and re-test; replace Stator if it fails the second test.

Tools: cylinder leak down tester, compression gauge

1. Remove spark plug and valve cover
2. Rotate crankshaft to TDC with both valves closed; lock flywheel
3. Attach cylinder leak down tester adapter to spark plug hole
4. Connect air source of at least 90 psi; adjust regulated pressure to 80 psi
5. Read cylinder pressure gauge; 20 percent leakage is normally acceptable
6. Listen for air escaping at carburetor (intake valve), exhaust (exhaust valve), or breather (piston rings)
7. For compression check, insert compression gauge in spark plug hole and crank engine until pressure stops increasing

Tools: VOM, oil pressure gauge

1. Check engine oil level, replenish to FULL mark if necessary
2. Set VOM to Rx1 scale and zero meter
3. Connect meter leads across switch terminals with engine shut down; should read continuity
4. Crank engine; meter should read infinity once oil pressure opens switch contacts
5. If contacts do not open, remove switch and connect oil pressure gauge in its place; start engine and measure pressure

Tools: VOM, thermometer

1. Remove Wire No. 85 from switch terminal and start generator to isolate the fault
2. Remove switch and place sensing tip into oil with a thermometer
3. Connect VOM test leads across switch terminals; should read infinity
4. Heat oil; at approximately 305°F (151°C) switch contacts should close and meter should read continuity