Cummins/Onan — Carburetor Overhaul
Repair & overhaul
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MCCK
Before you start
- Fuel leakage is a fire and explosion hazard. Do not permit any flame, cigarette, or other igniter near the fuel system. Forcing mixture adjustment screws tight will damage the needle and seat.
Procedure
- Disconnect all lines, linkages, wires, and attaching nuts or bolts; remove carburetor from engine.
- Remove air cleaner adapter, if equipped, and automatic choking assembly.
- Remove throttle and choke plate retaining screws, then plates. Pull out throttle and choke shafts, being careful not to damage teflon coating.
- Remove main and idle mixture screw assemblies.
- On downdraft carburetors, remove attaching screws and separate upper and lower sections. On sidedraft models, remove fuel bowl from upper body.
- Note float assembly parts, slide out retaining pin, remove float assembly, springs or clips, and needle valve.
- Unscrew and remove needle valve seat.
- Soak all metal components not replaced by repair kit in carburetor cleaner. Clean carbon from bore. Blow out all passages with compressed air.
- Check needle valve and float; replace if damaged or loaded with fuel. Replace old components with new parts from repair kit.
- Reassemble in reverse order; install needle valve and seat, bowl gasket, and float assembly. Check float level and adjust.
- Rejoin sections, install throttle and choke shafts and plates, center plates in bore, tighten screws.
- Install mixture screw assemblies, turn in until lightly seated, then out the specified number of turns.
- Reinstall carburetor on engine and connect fuel lines, linkages, and wires. Reset mixture screws.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Float level 1/8 in (see Float Adjustment)
Full service-parts list: Cummins/Onan MCCK →
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.