Generac — Engine Governor Adjustment
Adjustments · Mechanical governor
From a Generac service manual covering: IM100G, IM80G, NP100G, NP80G. Check it applies to your exact model before use.
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Procedure
- Connect an AC frequency meter across generator AC output leads.
- Turn OFF all electrical loads.
- Start the engine, let it stabilize and warm up.
- Check no-load AC frequency: 60.5-63.5 Hertz (60 Hz units); 49-51 Hertz (50 Hz units).
- For no-load governed speed: loosen NO-LOAD BUMPER SCREW lock nut and back off so governor is not pre-loaded.
- Adjust NO-LOAD SPEED ADJUST SCREW to obtain frequency close to 61.5 Hertz (60 Hz units) or 50.0 Hertz (50 Hz units).
- Adjust the NO-LOAD BUMPER SCREW to obtain 62 Hertz (60 Hz units) or 51 Hertz (50 Hz units).
- Apply rated load and check AC frequency under load.
- If frequency drops below about 58 Hertz (60 Hz units) or 49 Hertz (50 Hz units), adjust the DROOP ADJUSTMENT downward.
- If surging occurs when load is removed, adjust the NO-LOAD BUMPER SCREW inward.
Tools required
- AC frequency meter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- No-load frequency 60.5-63.5 Hertz (60 Hz) / 49-51 Hertz (50 Hz)
- No-load speed adjust to 61.5 Hertz / 50.0 Hertz
- Bumper screw to 62 Hertz / 51 Hertz
Source: Generac 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.