pettit

My Feedback: (23)

We seem to be having a problem keeping our Fuji 25 four stroke running for more than 50 seconds to just over a minute. It stops at any RPM, low or high.

Using an 18-8 Zinger prop, standard punp gas, 800 maH or 1100 maH ignition battery.

Hand starts sometimes but an electric starter gets it going immediately.

It acts as if the ignition just shuts off. But it can be immediately restarted and it'll run for another 50 seconds or so.

The engine was sent back for service and they said the carb was set a little too lean. They tested the engine, said it would idle at 1700, full power at 7100 but they didn't say how long it would run. They exchanged the ignition unit and gave us a new plug. The "adjusted" engine now runs for 50 seconds or so and stops, just like before.

Any ideas?

Bax

My Feedback: (11)

You may need to turn the idle and high-speed screws counter-clockwise a bit. Try 1/4-turn each. If the engine won't idle for long, it's likelly because the carb fills up when you prime, and then the engine burns it off when you start it. Work with the idle needle a bit at a time until you get sustained running. If nothing works, you may wish to send it in for service.

pettit

My Feedback: (23)

Problem solved! I set the engine on the test stand, fueled it and it started fine once the fuel got to the carb. It quit immediately after advancing throttle. Too lean. I richened it up a full turn, and it ran at high speed, but very rich. Back in half a turn and it was too lean. The needle is very sensitive but finally I got it to hold high speed running for 10 minutes or more.

You can't set the high speed "by ear". It sounds like it's "four cycling", which it is! Use a Tachometer.

You cannot run it too lean. It'll run poorly or not at all if too lean. It will not overheat if too lean also.

Bottom line: 2.5 turns out on the high speed to start and go from there in very small steps.

18-8 APC 6700 RPM, 1300 RPM idle all day long. Hand startable but electric starter recommended to get fuel initially to the carb.

Nice running little engine, great for a Balsa USA Triplane or Pup.

Thanks to Bax and to Greg Haun who called this morning to basically verify what I had found out last evening.

Bax

My Feedback: (11)

We're glad you got it solved. Usually, though, the needles aren't so far out of adjustment on a new engine, which is why we suggested the 1/4-turn.

bax