Cummins/Onan — Generator Disassembly, J-Series
Repair & overhaul · YD J-Series generator
From a Cummins/Onan service manual covering: 15.0YD-3G, 20.0YD-3G, 20.0YD-5DG, 25.0YD-3G, 25.0YD-5DG, 30.0YD-3G, 30.0YD-5DG, 6.0-3CS1, 7.5-3CS1. Check it applies to your exact model before use.
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Before you start
- Be careful not to let stator touch or drag on rotor.
- Do not hit bearing or windings.
Procedure
- Disconnect battery to prevent accidental starting.
- Remove end bell cover to reveal rotor-through-stud nut.
- Remove B1 lead from adjustable resistor in air outlet.
- Remove leads from control box to engine.
- Remove stator-through-stud nuts, end bell and stator assembly.
- Remove air baffle; turn rotor-through-stud nut to end of stud.
- Support rotor with hoist and sling; strike nut a sharp blow to loosen rotor from tapered shaft.
- Wipe clean and visually inspect all parts.
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.