My BME 44 has been a great running engine. On my third flight today, I was advancing the throttle in an upline and the engine sounded like it just wouldn't go past half throttle. I landed and checked the fuel and battery, and they were fine. I started the engine again (easy to start), but when I advanced the throttle it sounded like it was lean or something, and it would not spin up past half throttle, even though the throttle servo was fully forward. The engine bogged and then backfired, a first for this engine, and the prop and spinner were loosened. Tomorrow I'll be going through it, trying to find the problem. I had two previous flights today where the engine was flawless, then all of a sudden...
Any ideas of where to start looking?
Thanks
Sam

Ignition comes to mind...

Sure does.

So what kind of an ignition problem?

Loose ignition system connection?

High resistance/weak battery?

Timing has changed via moving pickup?

Defective timing module/chip?

Addressed to Ralph too.


Ed Cregger

Change of timing at the hub. Spark advance worn out. The 44 is not a new engine design and I suspect that the ignition has been in use for some time. Checking the timing is easy but prolly not the problem. Get the basic check out of the way so you won't have any doubts when you send the ignition oin or replace it.

Check the connector from the sensor to the ignition. The wire disconnected from one of the pins in that connector and caused the same condition in my BME 44.

First thing to check is the battery. Then plug it in directly to the ignition. Check the sensor wires and solder joints. If possible wiggle the wires while the engine is running at idle.

Keith
BME

Regarding the backfiring symptom, my friend has a BME 50 that started to backfire. The problem was eventually traced to a faulty hall sensor. Not sure if this could also cause your other symptom of not being able to throttle up.

Here's what today has revealed so far:
The plug had some chunky carbon deposits on it, so I cleaned and regapped it. The ignition would fire the plug when I turned on the ignition. When I spun the prop so the magnet passed the sensor, no spark. I pulled the sensor and located a wire (the blue one that is soldered onto the sensor mount - so I'm guessing it's the ground) that had broken. I resoldered the wire, reassembled, and still no spark when the magnet passes the sensor. The battery is a new battery, fully charged. Bypassing the swtich yields the same results. I've inspected all the wires to the sensor and after the ground was fixed, the others look okay. I'll try starting it later today.
Thanks
sam

Sam, do you have C&H or Falkon ignition? If you cycle the power on and off the C&H should fire and if so thats a pretty good indicator the ignition is working OK. If the C&H fires but not when you turn the prop its a good indicator that the sensor is bad or has a broken wire not making contact. I believe if you ground the white wire it will trigger the C&H to fire. If you have the Falkon you may want to send it to me.

Keith
BME

WORD

Thanks for all the good advice. I called Terry at CH and he asked if I'd gone through the trouble shooting routine. Whoops, had not done that yet. The ignition will fire when I turn it on, but not when I ground the white wire and then take it off ground. I was sure that since I'd found the broken blue wire on the hall sensor, that was the problem, but it now looks like it may be the ignition, or maybe both. So, I'm sending it off to CH today.
Keith: Terry says they have the sensor but not the mounting plate. This is my second sensor, and the plate CH provided last time is like a thick PC board cut to shape. I'm not sure if I can find (or if I even have) the old plate that came with the engine. Any chance you have a sensor mounting plate for the old BME44 in stock? If not, I'll re-use the PC board type one.
Thanks again
Sam

Sam we have about 2000 of them here. We can also supply you the bracket with the sensor on it.

Keith
BME

Keith
Sent you a PM re the sensor/bracket combos.
Thanks
Sam