Motorcycle Repair: 1982 yamaha 400, yamaha 400, petcock

Question
My motorcycle refuses to start unless jumped even though there is a new battery in it.  When  I do get it started it will only run if the choke is all the way open obviously feeding it to much fuel.  I have changed the spark plugs and battery and will be changing the oil and fuel filter in the next week.  What else can you think of that would help?

Answer
Sounds like u have more than one issue.  Let's deal with the choke first.  Jumping a battery increases the voltage no matter what, more volts = hottor spark.  Your bike is lean, check the jets for clogging and make sure the carbs r clean.

If u r fouling plugs then u have "flow by".  This is caused by gas filling the carbs then the piston chambers and then running by the pistons into the oil.  Turn off your gas when bike isn't running.  If u r already doing so, then make sure the petcock is functioning properly.  Good luck and let me know!