85 HD Sportster intermittent electrical problem (Page 1/1)
Mytime AUG 29, 02:35 PM
I thought I'd give the new forum section a try and see what you guys think. I've got an '85 sportster that has an electrical problem that's driving me crazy. Occasionally it will refuse to start, no spark. Anyway, if I let it just sit there for a minute or so, spontaniously, the ignition system will come back "online". The spark plugs will spark and ignite the fuel in the cylinders causing a rather loud explosion out the exhaust or carburetor depending where the piston is. Couple this with the fact that I was holding one of the spark plug wires the first time this happened and you could see this was almost an underwear changing situation! It will do this with absolutely no movement to the bike.
The ignition system is a simple one. It is electronic, not gap and capacitor, I checked the wiring, didn't find any loose wires or anthing worn through yet. I checked voltage readings and everything was what it should be where it should be. Nothing was grounding out anywhere. So that leaves me three components. Coil, pick up sensor or ignition module. One of them is bad. All are original so could have gone out.
Has anyone experienced something like this before? I'm thinking coil right now but don't know how to troubleshoot these without just replacing components.
nmw75 SEP 05, 12:12 PM
My fathers old 74 Honda had a similar problem.
Turned out to be a broken wire coming out of the headlight enclosure. Over the years, vibration & movement from steering caused the inner copper conductor to break. The outer insulation was fine.... Took lots of time with a voltmeter to track it down!
Electrical problems are the worst!

[This message has been edited by nmw75 (edited 09-05-2012).]