Bike sat for 3 weeks, went to start it this morning and it was completely flat. Tried roll starting it and couldn't get anything, then I jump started it off my car battery and it fired right up. I took the jumper leads off and it kept running, but when ever I rev it it starts missing and spluttering and the lights dim, connected the jumper leads up again and gave it a rev and it worked fine so it's definitely electrical issue. Put a multimeter on it while it was idling and was reading about 9 volts. I'm going to give the battery a charge overnight and try again tomorrow but can anyone tell me if its just a case of battery being too flat or maybe battery stuffed or something more like alternator not charging properly? I thought that if you got it started it should just run normally off the alternator otherwise you would never be able to roll start it if the battery is flat.