so my RVF 400 is not starting, I cant figure out why, when i turn the key nothing happens, no lights, nothing. when i push the ignition button nothing happens. so I tried to push start it and it would just make this horrible cranking sort of sound, so i tried to jump start it from a car battery, still nothing. This problem has happened before so i took it to the mechanic and he said all it needed was a new battery so he put a new battery in it and now 3weeks or so later (only ridden a few times because i was on holidays) it happens again. Can someone please help me?

Needs another new battery LOL. Seroiusly, what is the battery voltage, ignition switch off and then on.

yeah idk about the voltage but even if it was the battery shouldn't it still jump start off a car battery?

Agree, but if battery voltage does not change with ignition on then switch, main fuse or wiring issue exists. Main fuse is part of starter relay.

sounds like it may be main fuse if you have no instrument lights when the ignition is on.

last time my main fuse went was when the reg/rec packed in. try replacing the main 30A fuse, if it goes straight away then the reg/rec could be your issue.

also, measure the voltage across the battery - should be 12.3V to 13V if it's in a good way