I have a piaggio zip 53 reg slightly tuned mollissi 70

The bike is giving me a headache now when you ride it it will hit the powerband then will die down and only let you do 1/4 throttle after that and when you stop it will hit the band again then do the same thing!
I've replaced fuel lines added an inline fuel filter cleaned the carb fully left to soak overnight I've put a new air filter on it put new reed valve gaskets in it also cleaned reeds which weren't dirty but decided to anyway but when taking out the screws which hold the reeds in the screws were tight as f@&k ive taken the exhaust off and end can (stage6/and Leo vince exhaust) it had carbon build up around the exhaust packing but surely that wouldn't cause it and also I've took the head off and cleaned the piston and barrel from build up and I've moved the needle around no difference so I'm stuck now I think It may have something to do with the reeds.? Any help appreciated thanks!!


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Also I've checked the rollers (polini 9 roller vairiator) and they are fine no edges fully circle..


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Sounds like jetting problems to me