I just had an unusual problem flying today. During flight I lost throttle repsonse. I returned the throttle to idle and then the engine let out a big back fire, and then died. Upon inspecting the engine I found that the little screw on cap at the end of the spark plug had unscrewed itself allmost all the way off. I put loctite on the threads and screwed the cap back on. Placed the spark plug back into the engine. When I start the engine it wants to run backwards. I immediately quit trying to start it since hand starting a 22 inch prop that wants to run backwards is not my idea of a good time.

I have sent an email to BME, but I would hate to have to wait until monday for a response.

My assumption is that the back fire has caused a loss of timing or it has damaged the ignition module? Any ideas?

May have cut the flywheel keyand put the timing out. Pull the flywheel to find out. You may be able to make a temporary one.

This is a BME50 with CH ignition. There is no fly wheel. I have placed the engine at TDC and the magnet center is 4 or 5 mm just past the hall sensor. Can anyone verify if this is the correct position?

Is it possible that the loctite is interfering with the connection between the plug and the cap?

Snothead, you want the hall effect sensor to be about 2-5 degrees BEFORE TDC on the magnet as it passes the sensor. 4-5mm after the sensor is not correct and will lead to retarded timing and possible backfires, as well as power loss.

If the magnet is 4 or 5 mm passed the sensor when the crankshaft is at tdc then the timing is advanced about right. If you're talking about the magnet being CCW of the sensor and it sounds like that's what you're saying.

I have been in contact with Keith at BME both by email and phone. I have verified that my ignition is at 29 degrees BTDC using a timing wheel as suggested by Keith. While doing the timing tests my ignition switch fell apart in my hands. I think I have had a system failure in multiple places both in the spark plug and the switch to possibly justify my engine to run incorrectly. I have purchased a new switch and I just need the time to try the engine again. [img][/img] Keith at BME has been extremely helpful and responds quickly either by email or phone to any of the questions that I've had.

I replaced the switch and now the engine runs fine. Thank you everyone for your input. Thanks goes to Keith for his prompt support.