Cummins/Onan 4.0 BF-1R/9500 — Pistons and Connecting Rods Removal
Repair & overhaul
For the Cummins/Onan 4.0 BF-1R/9500, from the Cummins/Onan service manual.
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Before you start
- Avoid scratching the crankpin and cylinder wall when removing the piston and rod.
Procedure
- Drain oil.
- Remove cylinder heads and oil base pan.
- Remove the ridge from the top of each cylinder with a ridge reamer before piston removal.
- Turn crankshaft until piston is at bottom of stroke, remove rod bolts and lift rod bearing cap.
- Push rod and piston assembly out through the top of the cylinder using a hammer handle.
- Mark each piston and rod assembly and keep rod bearing caps with their respective rods.
- Remove piston rings with a piston ring spreader; remove retainer and push piston pin out.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
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.