Cummins/Onan — Adjust Carburetor Main Jet
Adjustments
From a Cummins/Onan owner's manual covering: 4.0CCK, 4.0CCK-3CR, 5.0 CCK. Check it applies to your exact model before use.
Applies to: Cummins/Onan 4.0CCK, Cummins/Onan 4.0CCK-3CR, Cummins/Onan 5.0 CCK, Cummins/Onan CCK engine
Procedure
- Connect full load
- Turn main needle out about two turns
- Turn in slowly until engine loses power
- Turn out slowly until smooth at full power
- Do not open more than 1/2 turn beyond maximum power
Tools required
- main adjustment wrench Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Do not open more than 1/2 turn beyond maximum power
Full service-parts list: Cummins/Onan 4.0CCK →, Cummins/Onan 4.0CCK-3CR →, Cummins/Onan 5.0 CCK →
Source: Cummins/Onan owner'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.