You don't tell us much about your modifications to the BWS engine.
It also sounds like your trying to install some strange chinese carby which is not a proper replacement for the standard Delorto carby. The proper larger Delorto carburetor is a straight exchange including the throttle cable and electric choke.
The other thing is the BWS 100 does not modify well and it won't go much faster without lots of other mods.
Its normal with these engines to use premix oil or both premix and the oil pump but there is skill plus trial and error in figuring out how much oil to use. more power via a different carby and the standard oil flows will wreck the engine.
Lastly, the seller of the carby should provide a new cable if its needed.
Youwill also need a set of jets for the new carby to reset the mixture.
A long time ago I had a BWS and found tuning the transmission was the best way to get cheap improvements in performance.
2001 Yamaha Zuma, DR Evo 68 cylinder, Leo Vince TT derestricted, Delorto 17.5 (#98 jet), standard aircleaner, RMS fan, Race CDI, Standard oiler and premix @ 75:1 Shell SX2, Doppler SR3 variator, RMS clutch, RMS R rear shock absorber and Pirelli SL26 tyres.