Motorcycle Repair: 2001 Honda Shadow Electrical, starter solenoid wiring, headlight circuit


Question
First off, i read your qualifications above and realize that you do not specialize in later models or cruzers but feel that you may be able to help me with my question.  So here goes...
My Shadow is a 2001, with approx 35,000 miles.  I ride the bike weekly, usually to work and it has served me well without any problems until now.  After riding to work 3 days in a row, i rode to a store and an hour or so later came out, got on it and it didn't want to start nor would the head light come on. It would barely turn over as if it had a bad battery. The battery is new and has been check out.  It's good.  
 It finally started but the head light wouldn't come on. After getting it home i notice that if i held in the starter button part way the head light would come on.  But not stay on.  What puzzles me is that the head light should come on the moment i turn on the key. It doesn't.  I would appreciate any help.
Biker Pete

Answer
Pete, it sounds like a failed starter button switch.

The switch has two functions....   

Button released (out) the headlight circuit is engaged at all times, as soon as the ignition switch is turned ON.

Button pressed (in) the starter circuit is engaged and the headlight circuit is opened up.

You do have the safety switch on the clutch bracket to check, but if the little plunger breaks off, then the switch goes into a default ON position, which would allow the bike to start in gear.

You might want to check the condition of the fuses, as they can fatigue over time and have tiny cracks develop which causes high resistance or just an open circuit even though they don't look like they are blown.

If the battery passed a fully charged load test, then problems can exist in the starter solenoid, wiring from the handlebar switches to the starter solenoid and there may be a diode in the starter circuit that needs to be checked.

You didn't designate whether the bike is a Shadow 600, 750 or 1100. Wiring should be similar but there may be some subtle differences between the models.

First thing is to test the starter button switch. They were a source of failures in the 1970-80s machines, but I haven't heard that much about them in later models. Still after 12 years and 35k miles, stuff can wear out and fail. The switches get hot internally due to the high current running through the tiny contacts. Sometimes the switch contact bodies just melt down inside the housings. You may have to undo a throttle cable to help get the housing off the handlebars and apart so you can see inside. Or do a continuity check with a 12v test light (hot) or VOM meter on ohms (ignition switch OFF). I suspect that the switch is dying, from what you describe.

There are Honda Shadow forums/websites which may have more info and/or wiring diagrams available for reference, if you don't have a shop manual.

Bill Silver