Motorcycle Repair: Honda c50 Electrical problem, honda c50, haynes repair manual

Question
Dear Mark, first of all I'd like to thank you for help your in my previous questions. Now, I have a problem with the electrics of my Honda c50. I run the motocycle with discharged battery for almost one year. I replaced the battery with a new one 2 weeks ago. After 1 week the resistance (the one placed on the motor of 4,2 Ohms) got burnt, and then followed the Head lamp.I replaced them with new ones but they also got burned. I thought it might be the rectifier, so I replaced it too. But the problem still exists. Note that the problem apppears only when I put the lights on(head lamp). I checked the wirings for short ciruits, but didn't find anything. Is there any 'trick' or 'tip' in finding short circuits? And is there some way to check the CDI unit? In Haynes repair manual it has a way for checking the CDI unit but it is not correct. The readings of ohmmeter do not have anything to do with the ones in Haynes manual, in a new (unsed) CDI unit. Well, the most important is some way to find the short circuit, because I think that that's the problem. Thank you in advance for your time and your patience.

Answer
Hi Panagiotis,

Check for clean, tight ground connections.

The lighting coil output is not getting regulated and blowing the bulb. Check resistors (regulator) and all ground connections. Look for corrosion and burn marks on switch contacts.

I don't know of any tests for the CDI.

Keep me advised.

Mark