by Jost Neeser
How many times have you watched a pilot at the field messing with the needle valves and struggling to get a new engine running properly. First flights can be nerve-wracking, and even more so when you aren’t confident that your engine will run reliably. Bench running your new four stroke on a test stand will greatly increase your confidence in your new power plant and will put the odds for a successful flight in your favor.
- Securely mount engine on the test stand.
- Set needle valves, high and low speeds to manufacture’s specs.
- Prime engine, put finger over carb, or choke until fuel is in the line.
- Set throttle to ½ or less. Adjust for rich mixture.
- Connect glow plug.
- Run for 1 to 2 minutes with glow heat. Shut engine down.
- Allow engine to cool. Repeat step 6 five more times, allowing cooling between runs.
- Run the engine for 3 to 5 minutes, allowing the engine to completely cool between runs, and repeat at least five times. During these runs remove the glow heat, and increase the throttle to full power for 1 to 2 minutes and return to ½ throttle.
- Open throttle to full. Lean the engine to its optimal setting by turning the needle valve until the RPM peaks. Richen the mixture by 200 to 300 RPM. Verify that this is the correct setting by momentarily pinching the fuel line. The RPM should increase back to the peak setting. Adjust the needle valve until this is achieved.
- The engine should be able to hold its setting for several minutes. If it doesn’t repeat step 8 until it does.
After the bench running continue break-in in the air, by setting the engine on the rich side remembering the engine will run slightly leaner in the air.