i just bought a monster moto 125 sx engine and it has no power i have a 26mm mikuni carb on but i kept the crappy stock exaust on which has a tiny 6mm hole in it to vent the gasses..so at half revs its fine but anything beyond that and it bogs realy bad i have tried everything changeable on the carb and stock works best but still bog loads should i change my exhaust or can anyone else think of the problem? thanks

 

probably just a low compression chinese scooter motor like most of them are standard,...try ordering a high compresion piston kit to wake it up.... that's if you've alreay got it jetted correctly adn everythign else..

 

thanks for the reply turboglen.It's jetted correctly and it came with a high compression piston,the problem was the crappy end can so i enlarged the hole from 6mm to 13mm and now it flies all the way through the rev range.
P.S it's not a scooter engine LOL

any advice on where i can get a good endcan cheap?