Lawn mower not charging the battery when running

[chevelle66]

Hi guys
    Can anyone help me out with this. I am wondering if these yamahas have a charging system and how they function. The battery runs down to 10 volts presently when running because of the electric fuel pump and the electric PTO. The PTO barely wants to turn on probably because the voltage is too low. How does the battery maintain 12+ volts and how can I look to repair the charging system. Obviously there is a generator or alternator I assume somewhere but I dont see an external one. Thank you for any help anyone can assist me with. I greatly appreciate it! Paul

[rattosh51]

Paul,
 Yes there is a charging system. It is a bit lengthy to explain, but is the same for all small engines and lawn tractors. Google "small engine charging system" and you'll get some insight as to how they work.
or click on this link...
http://home.howstuffworks.com/home-improvement/repair/how-to-repair-small-engines3.htm
There are some things you'll need to diagnose the problem, like a digital voltmeter.
10 volts is definitely a problem, and I'm surprised you can get the PTO on at all.
Read over the link info and come back with any more questions.