70cc aerox help

[sta00336]

I have a 70cc aerox/mbk o4 plate and recently i have noticed that it has gotten slower, it used to go off the clock on a straight but now it struggles getting to 50.
it will go to 50 mph at half throttle but as soon as i full throttle it, it just makes lots of noise but doesn't gain any speed (High revving?), it also sounds like it might cut out.

i have taken it to an independent garage and he said he came to a dead end with it as he didnt know what was wrong with it.

i have been told it could be many little things causing it but i wanted to see if someone could give me more proffessional advice. thanks

Im new to these so sorry for any things ive done wrong

 

[Lodewijk]

Does it run irregularly or "anxcious" when you have driven around a bit and then stop but leave the engine running.. dont know what the English term is, "running idle" or something..?

If so, then it is probably that your air intake has increased somehow, probably the air-intake-box had come loose from the carburator a little or has a crack in its casing, or the gasket below your manifold (or before it, at the carb.) has a crack in it.

If not, then try looking in your variomatic system. Perhaps the belt is at its end or your clutch has become defect.

 

[sta00336]

Err yeh it does run idle it sounds like it wants to cut out when it is just sitting there on tick over, and sometimes I will come to a set of traffic lights and then it will just cut out and will take some time
to get it going again. If that answers it ?