I'm restoring a 74' Honda MR 50. It now has a new piston, cleaned carb, and crankseals. The bike had been stored for 25 years, after it seized its piston.
The problem is the bike will start when stone cold, and run for about a minute. Then it dies and can't be restarted. I'm certain it is an electrical problem because there is no spark after the engine dies.
The bike uses a AC alternator that sends power thru a half wave recitifer, then into the coil.
The resistance measurements are a little off in both the alternator and coil.
I did a bench tested the coil, and found that the coil would not produce a spark until it got 1.3 volts. The coil then produced a weak spark. At 3 volts it would produce a strong spark.
I put a voltmeter in parallel with the coil to watch the coil input voltage. When I managed to get it to start the coil was getting .9 - 2.5 volts depending on rpm. The spark just died.
When measuring the resistance of the coil and alternator after it died I found no change.
When I bench tested the coil I let it run for 15 minutes at 3000 sparks / min without it shutting down.
I'm I missing something? I'm thinking there is something wrong with the coil despite the bench test.
Thanks for any help.
The problem is the bike will start when stone cold, and run for about a minute. Then it dies and can't be restarted. I'm certain it is an electrical problem because there is no spark after the engine dies.
The bike uses a AC alternator that sends power thru a half wave recitifer, then into the coil.
The resistance measurements are a little off in both the alternator and coil.
I did a bench tested the coil, and found that the coil would not produce a spark until it got 1.3 volts. The coil then produced a weak spark. At 3 volts it would produce a strong spark.
I put a voltmeter in parallel with the coil to watch the coil input voltage. When I managed to get it to start the coil was getting .9 - 2.5 volts depending on rpm. The spark just died.
When measuring the resistance of the coil and alternator after it died I found no change.
When I bench tested the coil I let it run for 15 minutes at 3000 sparks / min without it shutting down.
I'm I missing something? I'm thinking there is something wrong with the coil despite the bench test.
Thanks for any help.