Hard to shift into 6th

I've had the bike for a few weeks and could be a little better at riding it but this doesn't seems to be me. I have a very difficult time going from 5th to 6th and occasionally back down. Sometimes the bike is stuck in 6th until I can find the perfect rev match and it magically drops into 5th. I also get stuck "between" gears. Example: going from 3rd to 4th, the engine manages to end up in some neutral position.

I have noticed if I'm extremely quick with the clutch while up-shifting it's typically not a problem. There was one instance where the bike would not come out of 6th at all. I rolled over to the side of the road and played with the shifter and clutch until I was able to get to the lower gears and get rolling again. What's going on with this? I'm used to my vintage cafe that didn't care when you did a gear change at all.

Bleed the clutch. It sound like you have air in the system.

Comrade: Yes Agro is possibly right. Some people, myself included, have enlarged the jet slightly. From memory you can just buy a bigger jet possibly from a carby. Now the real trick is getting the jet out once it is loosened. I've found sucking on a bit of plastic hose to be very successful.

There are posts on this site as well. Use the search button.

Is the larger jet actually improve anything or it is for piece of mind only that it will not get stuck in the middle of the road?