Electrical Problem! Need help to track it down!!
Electrical Problem! Need help to track it down!!Posted a few months back about no spark at points or plugs and a constant short that blew the 15 amp fuse when I turned on switch to position 3. The bike has an aftermarket rectifier and accel harly coil on it. I installed new points, plugs, condensor and coil and the bike started and ran perfect for two days. Came out to the garage a couple of days later and it is doing the same thing as before. There appears to be a direct short when I turn on the switch, the fuse is blowing again and I have no spark. Is there something that could be trashing the electrical system and/or coil in such a short period of time. I need some trouble shooting help in a bad way as I do not know where to go from here!
I am no expert but....
What I would do first is to disconnect the coil, then put a new fuse in and turn the bike on to position 3. If the fuse blows again the short is before the coil. If not the short is coil onwards. If it is before the coil I would check the wiring in the headset, just visually make sure all the wires are connected properly and that nothing looks wrong (ie a bare wire etc). If the fuse does not blow then the short is further along the electrical system. Use a multi meter to check the resistance to earth of all the disconnected wires. One will show no resistance. This is your bad boy. If you post the results of this test I can help further, but the permuations of all answers are just not possible to write without the answer to these tests.
In an effort to isolate the problem I did as you suggested and the results are as follows. All test were conducted with the switch in position #3 regular daytime operation. Checked coil with multi meter and it rang out 2.8 ohm between primary and secondary wires, 12,750 ohm between spark plug leads and closed between the 12VDC terminals on the coil. No marking on coil for + or negative leads me to believe they are interchangable. When I describe what I found I call a "closed" circuit a "short" in my book. Correct my terminology if need be.
Installed new fuse with all wiring hooked up as normal and with points closed. Had 12.8 VDC on both sides of the coil and at the base of the points. Coil and fuse got hot to the touch from what I feel is a direct short. If the points have 12v on them and are closed against the other half of the points that are grounded to the engine is that not a direct short? Electric start would not turn engine over unless I jumped it from aux battery and when I tried to start her by kicking or electric start the fuse blew. Installed new fuse with all wiring hooked up as normal and with points open. Had 12.8 VDC on both sides of the coil and at the base of the points. Did not hook up aux battery and the coil and fuse did not get hot. As soon as I tried to kick her to life the fuse blew. Installed new fuse and disconnected all wires from the main switch in headlight. Jumpered between BAT and IGN and tried to kick her to life but blew fuse as in other mock ups. When I take out the fuse and put my meter into the red wire that goes to battery and into the main ground to the frame and turn the switch to #3 the meter shows the two circuits are connected which I call shorted out. Is my next step to start toning out wires one by one looking for a short. If so how does one handle wires that have a bulb in them and therefore show as a closed circuit.
Try disconnecting the two wires to the coil and seeing if the circuit is still closed.
If it is not closed I would try putting in a new (or different) coil. If it is still closed then it suggests that the short might be in the switch or the wiring from the switch. To test a ciruit with a bulb in it take the bulb out and check the power wire, the other wire should be earth anyway. I have had a short from a dodgy bulb.
Thanks for the suggestions greggie-e and I am pleased to report I got my baby running again. The problem did turn out to be the coil which I have temp replaced with a stock coil I purchased at a motorcycle boneyard. When I bought the bike it had a Accel Harley Coil on it and come to find out it had run for almost a year on a coil that was designed to be used on a ignition with CDI. Accel has a different part number coil for an ignition with points and I can only guess that the previous owner was sold the wrong retro kit. Hopefully someone else will read the post and avoid purchasing the wrong coil. The correct coil for a CA77 Dream would be a Accel #140403S/3 ohm service. Your suggestions and a little more patience on my end helped me track down the problem.
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