Cummins/Onan 1B Series / 1B Series Plant — Valve lifter adjustment
Adjustments · engine
For the Cummins/Onan 1B Series / 1B Series Plant, from the Cummins/Onan operator's manual.
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Procedure
- Remove tappet inspection and anti-flicker breaker point cover behind carburetor.
- Revolve crankshaft until intake valve opens and closes and piston is at extreme top of cylinder.
- Loosen valve lifter lock screw. Pushing in on valve lifter increases clearance; pulling out decreases clearance.
- Correct clearance for intake valve is 0.008 to 0.010 inch; exhaust valve is 0.010 to 0.012 inch when engine is cold.
- Thinner feeler gauge should pass freely; thicker should not.
- Tighten valve lifter lock screw securely.
Tools required
- feeler gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Intake valve clearance 0.008 to 0.010 inch cold
- Exhaust valve clearance 0.010 to 0.012 inch cold
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.