Generac 91401256S / Bsc 556 — Diesel Governor Adjustment

Adjustments · diesel engine injection pump governor

For the Generac 91401256S / Bsc 556, from the Generac service manual.

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Procedure

1. Start engine and warm up at no-load.
2. Adjust stop adjust screw to obtain correct no-load AC frequency, 62 Hz on 60 Hz units.
3. If hunting or erratic operation occurs, stop engine and turn stop adjust screw all the way out.
4. Remove plug at governor housing and turn governor adjust screw in about 4 clicks while holding stop lever right.
5. Install plug and turn stop adjust screw back to original setting.
6. Restart and check for hunting; repeat if needed.
7. Apply light loads in 10% increments to 50% and readjust governor adjust screw out one click if hunting occurs.
8. Apply 100% rated load and check frequency; should be 59-60 Hz, never below 58 Hz.
9. If low, adjust full load adjust screw in until speed increases, then back out until frequency drops, then in until frequency recovers.

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.

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