Got my buddies cbr600f3 together today and had it running for a minute. I have the gas line hooked up correctly and the gas is on, it has gas. I got the carbs set up correctly too. It ran for a few minutes, rev'd up just fine, then we shut it off. When he went to leave it started fine but when he gave it gas it died. It did that a few times and when the throttle was turned very slowly it'd rev up then sputter around 4k then continue to go up. But now it wont even start. Any ideas?

 

do you guys think it's a dirty carb? It's only been sitting for a month.