Motorcycle Repair: !981 Honda cb650 Custom, honda cb650 custom, head bolts

Question
This is my first bike. Purchased about one month ago. Have disassembled and
cleaned carbs but bike still does not rev above 6500 of it's redline of 9k. It
does seem to have plenty of power until that 6500k though. Has an irregular
slight backfire at varying times/gears/throttle position. It also has an oil leak
coming from what appears to be the head gasket or possibly valve cover. I
checked the torque on head bolts but that did not solve the problem. Bike
also does not not charge properly. Gets full 13.5 volts to battery at 3500 rpm
but less than 12v at idle. Have a Clymers but was disappointed at the lack of
help included on the topic of diagnoses. Any advice would be helpful. Thank
you

Answer
Christian, when the engine runs out of power or backfiring, apply a little choke.  If it runs better, you still have a carb problem and it's not getting enough fuel.  If it doesn't improve, it's probably an ignition problem.  It's pretty common for the headgaskets to weep oil.  The only way I know how to fix it is to replace the headgasket.

The charging system sounds okay.  It should have 13.5 volts when revved up and less at idle.  The alternator doesn't put out enough amperage to keep up at idle.

Regards
Rich