Motorcycle Repair: charging problem, stroke oil, volt battery

Question
Hey! I have a 1984 yamaha dt200r 2 stroke oil injected enduro, the battery does not hold a charge,but it runs without the battery just fine ,it also has the yeis/ypvs im only using it as a trail bike right now. I was wondering if i could hurt the engine in anyway without the battery ,and does the battery only run the lights .when i turn the key on i can here the yamaha power valve system operating.The bike runs like a charm and i dont want to wreck it.it only has 6 thousand on it.I hope that you can answer my questions cause  no one else can .And i checked all wires running from alternator and they seem fine what else do you think i should check for my charging problem. Thanks  .............  

Answer
You probably just have a bad battery.  Put a voltmeter on the battery with the bike not running.  Now start the bike and see if the reading increases 1 to 2 volts.  If it does, the bike is charging.  Remember a fully charged twelve volt battery will have between 12.8 and 13.3 volts. Yes your battery is just for your lights and it's not going to hurt your motor to run without it.  Even if your battery has 12 volts, if it can't handle a load it will drop and eventually go dead if you've got a bad cell.