Cummins/Onan — Slip Ring Inspection and Refinishing
Maintenance · Rotor slip rings
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Before you start
- Keep hands, fingers, clothing and jewelry clear of rotating machinery
Procedure
- Remove the air cleaner cover and air cleaner filter.
- Disconnect the lead wires from the brush block terminals; insulate and tie them aside.
- Remove the brush block mounting screws and lift out the brush block assembly.
- Insert a 3/8 inch allen wrench in the rotor through-bolt and rotate the engine one full turn, inspecting the slip rings.
- Crank the engine in 3 to 6 second periods, holding a commutator stone against the rotating slip rings.
- Remove the stone after each period and check that carbon and roughness are removed.
- Reinstall the brush block assembly and follow the Brush Replacement steps.
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.