50cc zip

[bizzy]

Hi, need your help 2 days ago i discovered that my exhaust had a crack in it( but it drove really good) today my friend welded the crack and fixed my exhaust i put it on. And my moped doesn't go past 20kmh it gets the power band in 1/4 throttle but when i give it 2/4 to 2/4 it sounds like its hitting the rev limiter like its making the power but the scoot doesnt go. What could this be?
Stock piaggio zip 50cc
17.5phva
Needle 4th clip
Main jet 78
Sito exhaust
Mind you a couple days it was good with the leak then i tried my friends yasuni z and it drove exactly the same as it now with the old exhaust but fixed. And sometimes when its on the stand when i give it full throttle it goes back to idle and after a second it dies out.

[gooddog]

maybe your exhaust is clogged. I couldn't really understand what you were saying about your friends yasuni z but check that the exhaust is clear and doesn't have an old wasp nest in it clogging it up. I drilled through a honda elite 50 exhaust and it ran like new. it was filled with carbon.