A clogged or worn-out Onan carburetor can cause poor engine performance, rough idling, or failure to start. Instead of replacing the carburetor, a rebuild can restore its functionality at a lower cost. This guide walks you through the entire process.
Signs Your Onan Carburetor Needs a Rebuild
- The generator won’t start or runs rough.
- Black smoke from the exhaust (rich fuel mixture).
- Engine surges, stalls, or struggles to maintain RPM.
- Fuel leaks around the carburetor.
- Poor fuel efficiency.
Tools & Parts Needed
- Onan carburetor rebuild kit (includes gaskets, seals, jets, float, and needle valve).
- Carburetor cleaner or ultrasonic cleaner.
- Small brushes, compressed air, and soft rags.
- Flathead and Phillips screwdrivers.
- Wrenches and socket set.
- Safety gloves and eye protection.
Step-by-Step Guide to Rebuilding an Onan Carburetor
1. Remove the Carburetor
- Turn off the generator and allow it to cool completely.
- Disconnect the battery for safety.
- Shut off the fuel supply and drain any remaining fuel.
- Remove the air filter housing and set it aside.
- Carefully disconnect the throttle and choke linkages.
- Remove the fuel line (use clamps to prevent spills).
- Unscrew the mounting bolts and take out the carburetor.
2. Disassemble the Carburetor
- Place the carburetor on a clean, flat surface.
- Remove the float bowl by unscrewing the bowl screws.
- Carefully take out the float and needle valve.
- Unscrew and remove the main jet, pilot jet, and idle mixture screw.
- Take off old gaskets, seals, and O-rings.
3. Clean the Carburetor Components
- Spray carburetor cleaner on all metal parts to dissolve fuel deposits.
- Use a small brush and compressed air to clean passages and jets.
- For deep cleaning, soak parts in an ultrasonic cleaner or a cleaning solution.
- Ensure that all fuel and air passages are completely clear.
4. Install New Parts from the Rebuild Kit
- Insert new gaskets, seals, and O-rings from the kit.
- Reinstall the main jet, pilot jet, and idle mixture screw.
- Attach the float and new needle valve, ensuring proper alignment.
- Secure the float bowl back onto the carburetor.
5. Reinstall the Carburetor
- Mount the rebuilt carburetor back onto the generator.
- Reconnect the fuel line, ensuring a tight fit.
- Reattach the throttle and choke linkages.
- Secure the air filter housing.
6. Test the Generator
- Reconnect the battery and turn on the fuel supply.
- Start the generator and allow it to run for a few minutes.
- Adjust the idle mixture screw if necessary for smooth operation.
- Check for fuel leaks and listen for any abnormal engine sounds.
Maintenance Tips for a Longer-Lasting Carburetor
- Use fresh fuel with a stabilizer to prevent clogging.
- Run the generator at least once a month to keep the fuel system clean.
- Regularly clean or replace the air filter for proper airflow.
- Drain the carburetor bowl before long-term storage.
Conclusion
A carburetor rebuild is an effective way to restore your Onan generator's performance without replacing the entire unit. With regular maintenance, a rebuilt carburetor can keep your generator running efficiently for years to come.