Cummins/Onan — Tappet (Valve Clearance) Adjustment
Adjustments · Valve tappets
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Before you start
- Downward pressure must be maintained on tappet so contact with cam lobe is kept.
Procedure
- Remove blower housing, valve cover and spark plug.
- Turn flywheel by hand to end of compression stroke; align T/C mark with 0 deg mark.
- Insert feeler gauge between valve stem and tappet.
- Turn adjusting screw until specified clearance is obtained.
- Exert downward pressure on tappet while measuring.
- If more clearance is needed, reverse procedure starting with smallest gauge.
Tools required
- Feeler gauge Amazon
- Standard automotive type wrench
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Intake .011 in
- Exhaust .010 in
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.