Cummins/Onan — Adjust valve clearance - Two-Cylinder J-Series engines
Adjustments · Valve train / rocker arms
From a Cummins/Onan service manual covering: 10.0JC, 12.5JC, 15.0JC, 4.0JB, 5.0JB, 6.0JB, 6.1JB, 7.5JB, 7.6JB. Check it applies to your exact model before use.
Applies to: Cummins/Onan 10.0JC, Cummins/Onan 12.5JC, Cummins/Onan 15.0JC, Cummins/Onan 5.0JB, Cummins/Onan 6.0JB, Cummins/Onan 6.1JB, Cummins/Onan 7.5JB, Cummins/Onan 7.6JB, Cummins/Onan JB engine, Cummins/Onan JC engine
Procedure
- Turn flywheel until cylinder to be adjusted is on its compression stroke
- Turn flywheel until TC mark lines up with timing pointer, then turn clockwise an additional 10 to 45 degrees
- Check cylinder head-bolt torque (see Fig. 60)
- Using a feeler gauge, check clearance between rocker arm and valve
- Increase or reduce clearance until proper gap is established, adjusting with the locknut
- Refer to Table 3 for correct valve clearance setting
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 28 to 30 lbs. ft. head bolts
- Valve clearance per Table 3
Full service-parts list: Cummins/Onan 10.0JC →, Cummins/Onan 12.5JC →, Cummins/Onan 15.0JC →, Cummins/Onan 5.0JB →, Cummins/Onan 6.0JB →, Cummins/Onan 6.1JB →, Cummins/Onan 7.5JB →, Cummins/Onan 7.6JB →
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.