FZR400 - won't stay running without booster pack

[Straycat]

Hi Guys, I know the battery on my FZR400 is weak (and im getting a new one). I fired it up today using a booster pack on the battery. It started ok, and ran ok until I shut the booster pack off and then it dies immediately.

Thoughts?

Why does low voltage cause it to stall immediately ?

Just the battery ?, Reg/Rec ? (which I can only properly test once a new battery is in otherwise im just getting a reading from the booster pack)

[snydes]

Check voltage coming from stator on the battery. Should be around 14V. If not, check actually voltage directly from stator measuring across each pole (AC system). If ok, the you're regulator or rectifier may be bad. If it's the original one I'd just replace it. People commonly go to a newer R6 full aluminum style.
But also, get the new battery it may not even be able to take a charge anymore