Electrical Issue... Death by Start

Ok, I have a weird electrical question on an 81 xj750 and I don't even know where to begin. If I let my bike sit for a few hours, go out and turn the key to on, the bike lights up like it should. When I hit the start button however, I hear a click come from somewhere around the battery and then all lights go out and the bike does nothing (headlight wont come on, instrument cluster stays dark, no neutral light, etc....) Again, if I let it sit for a few hours I can recreate the same scenario. I have tried recharging the battery and charger indicates the battery is at around 12.5 volts and 100% charge, but as soon as I hit that start button its lights out for my baby! Please help!

 

Clean & tighten all connections to the battery, starter & ground.

 

...and th general consensus is that if you have th original glass type fuses/holder they are best repalced with blade type holder/fuses, at least have a look at what yours are like, it maybe ok. Plus what wiz said < easy...
..less easy but not hard to do > Could also be that th starter needs a clean out.

 

poor or corroded battery connections.

the starter won't cause the lights to go out and not come back on.

in the old days when cars had top post battery connections. it was a common problem. loose connections or corrosion. hit the key, lights go out. wiggle the battery connections, lights come back on.

my own car did the exact same thing 2 weeks ago at the gas station. the positive side post connection was coming loose.

 

Thanks all for the replies! Unfortunatly I work pretty late, but I will try to give the terminal a good cleaning tonight. The don't look corroded and felt pretty tight, but may as well start with the easy stuff. As far as the fuse box goes, my bike actually lacks one lol. The PO actually pulled the stock fuse box and replaced it in line blade fuses. I of course checked those and none were blown. Although he may have installed it incorrectly, I am leaning towards it being ok since I rode all of last summer with no electrical problems what so ever.

 

OK, so actually had time to go out and take a quick look at the bike this morning. I cleaned the terminals to and reinstalled the battery. turned the key and nothing, no power. I decide to hook up charger and it read the battery at 12.5 volts again with about an 85% charge. I let it get back up to 100%, but after disconnecting the charger and turning the key,I still get nothing. Are there other fuses other than the ones under the seat. I have four blade style fuses under there but none look blown. Any more ideas?

 

Great News. I went out and played around with bike for a while again and this time followed the ground cable to where it was actually grounded. The connection was tight but when my wrench made contact there was a nice spark and viola... power galore! I hit the start button and the engine started cranking. I let the bike idle for a while and warm up (its about 40 out right now and it has not ran all winter) and was actually able to go for ride! Best feeling in the world! Off to the next adventure! Thanks fr the help guys!

 

glad you got it running. now come put mine back together. i'm getting lazy in my older age.