I start My 2007 v star 1300 cold it starts right up put in gear its fine but when I hit the throttle it shuts down then it won't start back up on it own anymore I have to keep throttling to keep the bike running or else it shuts off what do you think it is a sensor or what?

Check out the switch on the stand if it is faulty or out of position it will cause engine to shut down when you select a gear,
let me know how you get on

Take one spark plug out, connct it to its wire and lay it visible on the engine, press the starter and see if there is a spark.
No spark; check if there is power to the ignition coil, if power there, coil is bad.

Engine stalls or RPM fluctuates at idle up and down or dies near idle.

This problem is commonly caused by a dirty automatic idle speed control valve and throttle valve but always run a OBD2 fault code as well as the cleaning procedure. Buy a can of throttle valve cleaner (do not use carburetor spray cleaner!) from NAPA or Carquest (made by CRC chemicals) and spray it into the air intake while the engine is running, use up about 1/2 the can, engine will try to stall hold the speed up, shut it down and let it soak for 30 minutes, restart and blow out the remaining fluid, shut it down and disconnect the negative battery cable for 5 Min's to reset the base idle control

Your best bet is to purchase a shop manual if you plan on keeping the motorcycle and perform repair and maintenance on it.
http://clymer.com/SearchResults.aspx?t=V%20Star%201300&y=2007&mid=337&mn=Yamaha&

look under the kickstand an see if your switch is disconected there may be a broken spring that is not letting the switch move to the on posistion the only other thing that i can thank of off hand is that your kill switch may be bad but im leaning toward the kick stand switch can you put it in netural and the bike roll freely if you can then its the switch if the switch isnt depressed then the bike wont start hope that helps. [email protected]

Can you hear the fuel pump? If not then it will need to be replaced also check the fuel filter they will clog up some times. The other thing is check the fuses for the injection system. and you can also unplug the injectors and test for power at the injectioner.