Cummins/Onan B43 / B48 — Carburetor Overhaul

Repair & overhaul

For the Cummins/Onan B43 / B48, from the Cummins/Onan service manual.

Applies to: Cummins/Onan B48

Procedure

1. Remove air cleaner and hose.
2. Disconnect governor and throttle linkage, choke control and fuel line from carburetor.
3. Remove the four intake manifold cap screws and lift complete manifold assembly from engine.
4. Remove carburetor from intake manifold.
5. Remove main jet and idle adjustment needle (and throttle/choke plates and shafts on all other carburetors).
6. Remove attaching screws and separate upper and lower carburetor sections.
7. Note position of float assembly parts, pull out retaining pin and float assembly.
8. Remove needle valve (and unscrew needle valve seat).
9. Soak all metal components not replaced in carburetor cleaner; do not soak non-metal floats.
10. Clean all carbon from carburetor bore; do not plug idle or main fuel ports.
11. Dry out all passages with low pressure air (35 PSI).
12. Check adjustment needle, float, and choke/throttle shaft play; replace worn parts.
13. Install needle valve, main jet and float assembly; check float level and float drop.
14. Position gasket and install upper carburetor section, idle adjustment screw, throttle stop screw and fixed main jet plug.
15. Mount carburetor and manifold on engine, reconnect hoses and linkage, then adjust carburetor and governor.

Full service-parts list: Cummins/Onan B48 →

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.

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