Cummins/Onan 4.0 BF-1R/9500 — Carburetor Adjustment
Adjustments
For the Cummins/Onan 4.0 BF-1R/9500, from the Cummins/Onan service manual.
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Before you start
- Do not open main fuel jet more than 1/2 turn beyond the maximum power point
- Forcing the needle against its seat will damage it
Procedure
- Turn main fuel jet 1-1/4 turn off its seat and idle fuel jet one turn off its seat to permit starting
- Readjust them for smooth operation
- Set throttle stop screw with no load connected; turn adjustment until unit runs at 1500 rpm
- When stop released, governor controls no-load speed at 1850 to 1890 rpm
- Allow engine to warm up before final adjustment
- Adjust idle fuel jet with no load connected
- Open main jet until engine runs smooth under acceleration with no load
Specs & values
- Idle fuel jet one turn off seat
- Main fuel jet 1-1/4 turn off seat
- No-load speed 1850 to 1890 rpm
Source: Cummins/Onan 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.