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Cummins/Onan 4.0BF-1R/9500 — Engine Assembly

For the Cummins/Onan 4.0BF-1R/9500.

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Before you start

  • Use only genuine Onan parts and Onan special tools when reassembling your engine.
  • After the internal engine parts are assembled, the engine should turn over by hand freely.

Procedure

  1. Use the proper bearing driver to install front main bearing after coating it with a light film of oil.
  2. Insert rear main bearing in rear bearing plate.
  3. Install crankshaft and rear bearing plate.
  4. Install connecting rods, pistons and bearings.
  5. Install camshaft and gear.
  6. Install valve assemblies.
  7. Install oil pump, oil base and cylinder heads.
  8. Install breaker box.
  9. Install fuel pump, oil filter, starter, generator, carburetor, fuel lines, spark plugs, etc.
  10. Install crank gear, aligning crank gear mark with camshaft.
  11. Install gear cover and oil seal.
  12. Install flywheel alternator stator.
  13. Install flywheel.
  14. Install all housings, air cleaner, control box, etc.
  15. Reinstall power plant in vehicle, making proper fuel, battery, electrical and exhaust connections.
  16. Fill crankcase with oil.

Tools required

  • Bearing driver
  • Torque wrench

Source: manual:965-0515 Onan 4kwBF RV Genset Major Service manual (09-1973).pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.