Hey guys, i'm a newcomer to this forum/website and i'm a relative newcomer to roadriding. (Done a bit of Motocross). I recently purchased a 1991 CBR250RR from a private seller. For the first two months the bike started fine (Abit of trouble in the mornings though). It just needed a bit of choke occasionally. In the past few days the bike has ceased to start. The engine does turn over (It was coughing and spluttering yesterday but wouldnt start up, now it doesn't even do that). The battery is fully charged. The killswitch is set to 'ON'. There is petrol in the tank. Any tips on what could be causing the issue/how to fix it? Me and my Dad are in the process of taking the bike apart, he think's the fuel vacuum might be causing the issue. Ps, another quick question. After taking the air box off, and looking at the carbs from aboce, there are several silver valves with a small opening above the butterfly valves controlled by the throttle. Does anybody know what these valves are, and what controls them? Thanks in advance!