Cummins/Onan — Timing Gears Service
Repair & overhaul
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MCCK
Before you start
- Do not press on the center pin or damage it in any way.
Procedure
- If replacement of either crankshaft gear or camshaft gear is necessary, install both gears new, never one only.
- Use a gear pulling ring to remove crankshaft gear; remove snap ring first.
- Camshaft gear is pressed on and keyed to camshaft; remove camshaft and gear as assembly after removing crankshaft gear lock ring and washer.
- Before removing camshaft and gear assembly, remove cylinder head and valve assemblies.
- Remove operating plunger for breaker points. Remove fuel pump and tappets.
- Press camshaft out of gear using hollow tool or pipe fitting over camshaft center pin; do not press on center pin.
- When pressing camshaft gear onto camshaft, ensure gear started straight and key properly in place.
- Install governor cup assembly before installing camshaft and gear in engine.
- Ensure 'O' marks on timing gears coincide exactly when gears installed.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Timing marks 'O' must coincide exactly
Full service-parts list: Cummins/Onan MCCK →
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.