Most stock pipes only work to 8,500 RPMs where performance around 10,500 and racing 14,000 . Here is a great article on 2T exhausts
http://49ccscoot.proboards.com/thread/1391 Leo Vince is a great brand and worth the extra money . My scooter dealer has a Yamaha with a 70cc and LV HM70 pipe and its a wheelie machine and not too loud . I have a PM Racing pipe and its louder than a Yamaha YZ 80 as at top speed it makes my ears ring and echoes off large trucks and buildings . Takeoff was less since its not restricted and does not build up backpressure but midrange and top end it zooms .
What mm is yourcarb ? Most have a 17.5mm but mine has a 19mm TK and works great for the BBK and when it was a 50 . Do you have the airbox and stock pipe ? I have a Uni airfilter and use a 120 MJ since I live just below The Blue Ridge Mountains and its so darn humid at times . I like to run just a hair rich to be safe rather than dead on it . Stock it had a 68MJ and I put in a 75 . I installed a small Uni vent cover around half the size of the big red Uni and it ran like a boss with a 90 MJ . I bought the proper Uni and my dealer and all the other scooter and motorcycle shops in town ( over a dozen ) none had Mikuni VM11/22 MJs . Well being impatient I put it on anyways . It had just a slight bog but not like anywhere close to stalling and dang it the engine seized in less than a 1/4 of a mile going around the block . I would get a jet kit like this
http://www.partsforscooters.com/114-...ategory=133078
I use NGKBRP8HIX the iridium .
Do you use the oil injector or premix ?