Pressing the electric starter kills all electric

[amc3]

Hi Folks,

I'm coming into my 5th season with a 1979 XS400, my first and only bike ever.

It's been a great bike, with only minor issues that I've always been able to address on my own. But now I'm stumped.

Pressing electric start button makes a single "click" sound and then all electric is dead--no dash lights, headlights, horn, signals, etc.

Once this happens, the only apparent way to get electric back is to disconnect the battery terminals and then reconnect them. That sounds like voodoo, so might not actually be what's getting the electric to come back. But it seems to work.

In the meantime, I'm forced to always use the kick starter, which isn't terrible but also not ideal.

What's going on? Seems like some kind of short but with electrical being the most mysterious part of the bike to me, I could use some ideas on where to start.

Thanks!

 

[rshutchinson]

Sounds like a dead battery or bad/dirty ground.

What is the volts at the battery before, during and after you press the start button?

I'd try sanding the terminals of the battery and connections to the battery to clean them up.

 

[amc3]

Thanks rshutchinson.

I don't have a voltmeter. But I can tell you that this happens even after it's been sitting on the battery tender overnight. I can try cleaning the terminals but would that also fix the bad/dirty ground?

 

[rshutchinson]

Even a bad battery can be charged to show 12+ volts when sitting, it's when a load is applied that it fails. May want to pick up even a cheap voltmeter to do some testing.

If it is a bad ground it could be at one of the terminals to battery. In fact, I'd just do them all. Look for the starter solenoid and clean those 2 terminals. Then follow the ground down to the rear of the engine under the carbs. There is an engine ground there, clean that as well.

 

[xschris]

I would look to the starter button, starter relay and all connections related.

 

[Big D]

After a period of time do the electrics come back on until you press starter button again? If so, I would suspect a starter relay or the starter .... but check battery first.... [emoji6]

P.S. This is a handy item for any garage.... I installed a set of smaller clamps to make it more motorcycle friendly.

http://t.harborfreight.com/100-amp-612v-battery-load-tester-61747.html

 

[amc3]

Thanks a ton, rshutchinson, xschris, Big D.

I'll give these a shot this weekend or next and report back.

 

[Wolfe_11B]

Slightly off topic, but are you into AMC's? Or does the user name have another meaning?

 

[XS400NJ]

I would take jumper cables and connect to a working car battery; if bike starts - you know that starter and connections are good. Chances are your battery is weak.

 

[amc3]

Finally got a chance to put time into this today. I cleaned and sandpapered connections to the battery and then (most importantly, I think) I disconnected the grounding connection to the engine block (where I was surprised to find such a long bolt). That bolt's threads were pretty darn rusted. Cleaned the threads up, screwed it back in, then for fun, unscrewed it again, and found that it had picked up rust from the inside again. Cleaned it again, repeated this about six times until it came out clean.

Gave the electric start another try and voila!

You guys are great. I've cleaned the battery terminals in the past but had never thought about the ground--especially since it looked clean from the outside on the engine block.