XS400 STarting problem

[phatdoughnut]

I have this 1981 XS400, shes been a good bike but she quit on me the other day. I got her home and i started testing things.

1st - i jumped the bike and started right up, once i un hooked it, it died.

2nd - i noticed the headlight wasnt lighting up, so i tested to see if the conenctor had power and it does.

Does the headlight work as a fuse or something? the headlight has always worked until this point.

Thanks for all the help.

[GNEPIG]

.. how old is your battery? it sounds like your battery is finished.
also, how many miles are on your bike? after about 13,000 miles the stators on those bikes take a dookie.. sorry man, it's the vibration.

[phatdoughnut]

It has a little over 12,000. I thought if the stator was bad, it wouldnt start period? I guess it could be the battery too

[Stratus311]

It sounds like it's generator/alternator related. The actual trigger for the headlight comes from the generator. There is a small fusible link in a clear plastic heatshrink somewhere on the wire harness. Keep the bike jumped, while running, check voltage to the battery and see what the output looks like.

[phatdoughnut]

would the fuse be under the seat? or in the headlight? i couldnt find anything in the headlight. And when i tested the headlight plug, all 3 wires going to it had juice. Ill test to see what the voltage is on the battery.

My dad seems to think it might be the voltage regulartor, he sais they go out alot on older bikes.

Thanks for all the help.

[Stratus311]

Well, if the connector to the headlight has juice, it's just a dead bulb. Get a new one.

As far as not running, I don't think it would be the regulator. If it fires up when you have it jumped, then it could be a dead battery. Old batteries hold very little voltage and electronic ignition XS400's NEED a charged battery to run. A new battery is only about $40. Try that if you can. Otherwise, still try and let me know what the voltage is at the battery when the bike is actually running.

[randy]

phatdoughnut,

All three wires at the headlight bulb can't have juice. One of them has to be a ground, the other two are low and high beam hot.

[phatdoughnut]

Im sorry thats what i ment, i was just in a hurry trying to type it. Yes the ground works, and the two hots work when i have my test light ground(one with the hi off and vise versa.)

I jumped it again today and it read 12v's as soon as i hooked it up the volts dropped. I guess ill just try to find a stator, get my battery checked at the parts store.

Thanks for the help.

[Stratus311]

Did the battery read 12 volts BEFORE you hooked it up to the bike? What is the voltage to the battery with the bike RUNNING?

[phatdoughnut]

The problem is that as soon as i unhook the jumper cables the bike dies. I have my volt meter hooked up and you can see it go from 12vs to 2 volts in a matter of seconds.

[Stratus311]

Throw that battery away. That thing is dead as a door nail. It's very possible that the battery has developed a short internally.

[phatdoughnut]

okay, ill go get a new one today.. sweet