Cummins/Onan — Generator Assembly, 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
- Keep B1 lead short and away from the blower.
Procedure
- Clean and inspect all mating surfaces.
- Coat mating area between bearing and end bell bearing hole with a thin film of Molykote.
- Install rotor-through-stud in engine crankshaft and install key.
- Slide rotor over through-stud and onto crankshaft.
- Install baffle ring.
- Install stator through-studs in adapter.
- Install stator and end bell; torque nuts on through-studs to 19 to 21 ft-lbs (26 to 28 Nm).
- Torque down rotor-through-stud nut to 55-60 ft. lb (75-81 Nm).
- Tap end bell to align horizontal and vertical; recheck torque.
- Reconnect leads to preheater, centrifugal switch and governor solenoid.
- Install lead B1 on adjustable resistor R21.
- Install end bell cover.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Stator through-stud nuts: 19 to 21 ft-lbs (26 to 28 Nm)
- Rotor-through-stud nut: 55-60 ft. lb (75-81 Nm)
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.