P200 won`t rev out...help...head fried

[Bofs]

I`m working at a bog standard PX200E(mid 80s one) at the minute and it`s doing my nut in.
It`s had an engine rebuild, new crank and bearings and all, it rattled like a hewer before the rebuild.
It just won`t rev out on full throttle(had this problem before the rebuild too), it goes a bit boggy like a slight misfire, holding back, as if the choke is on a bit.
It`s the same in each gear, not just 4th. I`ve swapped out the stator, CDI, lead,cap and plug but still the same. It had a 118 main in it, changed to a 116, still the same.
It felt like an electrical problem but I also have cleaned the carb in an ultrasonic cleaner to make sure it`s not the airways.
Just wondering has anyone come across anything similar before?

[Spanish Fly]

Blocked exhaust?

SF

[john.t5]

Fuel pipe too long? Had that but only effected bike in 3rd and 4th.

[Bofs]

New exhaust fitted, pipe length ok. Just got it sussed after a wee rip down the road it`s revving clean now.
The air filter was starting to come apart so tried it without, revved nice. Ran it with the filter again...crap so replaced it with a sound one, problem cured now. A fekkin air filter after all that...sweet Jesus