Recently bought an aussie model cbr250rr... The bike will not start first time. It takes many start or a choke with some throttle to get her going. She might stay on for a little bit before the engine just cuts out. Once I'm riding however everything is fine and I can turn her off and on again no problem without the choke. Recently I had an off in a car park after riding for a while and I had to use the throttle and choke again to start her but normally once the bike is warm its no problem to start her up. The previous owner would put in premium and that's still in the tank and I've heard that can cause problems.. like blocking the carburetor?