Cummins/Onan 6GO — Tappet Adjustment
Adjustments · Valve tappets
For the Cummins/Onan 6GO, from the Cummins/Onan operator's manual.
Applies to: Continental Red Seal Y91-273 or Y91-264 engine
Before you start
- Tappets set too close may cause burned or warped valves, seats, and scored tappets or camshaft lobes.
Procedure
- Remove the valve chamber cover to reach the tappet adjustments.
- Crank the engine by hand until the intake valve opens and closes; both valves for that cylinder will then be closed.
- Set the adjusting screw clearance to 0.012 in for both intake and exhaust valves.
- On engines with Roto type exhaust valves, set the exhaust valve tappet clearance to 0.010 in.
- Securely tighten the lock nut on each adjusting screw.
- Make a final check with the engine running at idle speed.
Tools required
- Three wrenches Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 0.012 in intake and exhaust
- 0.010 in Roto exhaust valves
Source: Cummins/Onan operator's 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.