Are we talking about bolt #12 that holds the gear change actuator arm #3 to the gear change actuator shaft #8? If that is loose, you need to pull the engine. If that was loose, you would probably have problems shifting in more than 1 gear.
I would suggest you have some worn dogs on 2nd gear. This also requires an engine pull. You could get the dogs undercut like many fellows have done. Here is a thread recently addressing a 2nd gear issue due to worn dogs.
I have 2011 roadster. All gears are working fine and Shifting up and down very smooth except when I hit the full throttle at 2nd gear only it's cuting off and on on!!
Also, Kevin is asking about the amount of freeplay you have in the clutch lever. Rockets are temperamental if they don't have around 2 mm there. No freeplay also causes premature wear in the clutch lifter shaft mechanism.