running problems

[king1]

My bike is running like a bag of s##te
At normal speeds it is ok but at motorway speeds
the engine is like it is stuttering
no power
power even drops off
you start off with a full fuel tank and it drops down fast, when you open it there is a fair vacuum

at the moment I am tuning in the carbs and building a balancing tool, to check the balancing
all my local garages are not interested in looking at it

What do I need to look at and do???

Thanks
you can tell a happy biker by the flies in his teeth