This has been happening for a few months now, when you turn the key on and the tach swings over to 14k and back. Mine will sometimes flutter on the way up then stop and come back to zero where it flutters a little more. A new spin was the tach didn't work at all even when started for at most 20 seconds before it showed a reading. I didn't think too much of it at first until a ride home from work to the gas station left my bike dead as a nit after refueling. I jump started it with no problem and took it home where I put the battery on the trickle charger, it went green almost immediately.
I've talked to some people where they said that's a sign of a weak battery, so I bought a new one. First few days I noticed no problems and then it fluttered again, so obviously it wasn't the battery. Although I do think it was getting weak, if the bike sat idle for a few weeks there wasn't enough juice to start it.
Has anyone come across this before? I'm hoping it's not too serious a problem.