Hi got a bit of a problem with my bike, its a 2001 gas gas 280 txt pro and was in a bit of a state when i bought it a couple of weeks back. i have spent a lot of time and money getting it running again but there is something wrong and i cant figure out what it is. the bike will start fine with the choke on but when i turn it off the engine cuts out, also if i rev the bike it cuts out instantly. Any help greatly appreciated!