I've had a BME 50 for one and a half years now, and it has always started and ran flawlessly. However 2 weeks ago it started giving me trouble. Normally, with the choke on and 4-5 flips it coughs and then choke off, 4-5 flips and it starts. Now, it coughs as always after a few flips with choke on, but when I remove the choke and flip it, I am unable to obtain more than a few coughs. I can repeat this process indefinitely, choke on, cough, choke off, more coughs, etc.

I've checked the spark, beautiful. I mixed a new batch of fuel in case I had a bad one, no difference.

I managed once to get it started after 1 hour of hard labour, and it ran beautifully. But after the flight, I couldn't get it started again.

Any idea of what might be the problem ? maybe something to do with fuel delivery ?

Gabriel

Check the filter screen in the carb, under the cover with 1 retaining screw. It is a very fine screen and will clog after a time. Also if you have not done so, replace the plug. Sometime a weak plug will not fire as hot under compresion. Be sure to use the correct resistor type plug.

thanks, I'll try that.

I recently had the same problem with mine. Turned out to be the fuel tubing was hard (old) at the tank nipple and sucking just enough air to prevent it from starting. I had the same symptoms as you.

Were you seing any air bubbles in the fuel feed ? I have removed the cowling on the plane, and I can't see any bubble in the line. However you are right, it might be a good idea to check my plumbing while I'm at it.

No, I didn't see air bubbles.

I swore it was going to be an ignition problem at first.

Most definitely(in my case) was the fuel line.

well, turns out the problem was the plug. Even though I could see the spark fine with the old one, I replaced it and the engine started fine. It's a simple fix, but it took me 1 week and a half just to locate this particular plug (BPMR6F)! Nobody had one in stock. I ended up ordering one from the Internet

Thanks for all the replies

Gabriel

Gabriel, it's very interesting that you mentioned this problem. About a week ago I had the identical problem on a Sachs 4.2. When cold it would start good and run good. Shut the engine off and I couldn't get it to restart no matter what I did until it got back to ambient air temperature. I pulled the plug, some kind of Bosch, and it looked very good with a light tan color. I replaced it anyway with a new Champion RCJ-7Y. Problem solved. Wish I had done that about 3 hours sooner.

I would like to hear a good explaination as to why it will start good cold and run good but will not start hot. Or maybe even a good theory. What does a "weak" plug mean? Weak how? I understand what a weak battery is but not what a weak plug is.

Ken