1982 kz440 wont go over 45mph

So I have finally got my kz440 running and rideable. As I rode it today it would not go over 45mph. It would start to bog down around 4000rpm no matter what gear I was in....is this a fuel/air problem? Or am I missing something?? 

Likely fuel related.  Any mods?

No mods, completely stock. The one thing thats odd is the left carb was dripping a bit of fuel after about an hour of riding....im gonna try the clear tube method later today and see if the furl levels are off. 

Probably dirty carbs.  Clean them thoroughly and see if that cures the problem.  Ed

If the bike has mechanical timing advance weights, make sure they are not stuck.

It turned out the fuel/air adjustment was off by about a 1/4 turn. Tuned it and it ran great!! So glad to be able to ride this bike!! I have been looking at it in my father's garage for the last 15 years and it is finally rideable! Its not perfect but it was free and it is my first bike. Just gotta get a new coat of paint and put the emblems back on and I think it'll be a beauty!

Gotta love easy quick fixes. She looks great!