Which 150 engine did you start with? A yx 150 ?
Weldangrind, they make a 190 cc horizontal 4 valve engine called the Anima from Daytona.
It puts out around 22hp with a good carb & good exhaust as it wants to breathe.
That engine is a beast but I don't know it's reliability in a street bike for longevity.
People are using it their street bikes but they may not be daily drivers.
http://daytona-global.com/products/?...&subcategID=10
Dyno run with its baby brother the anima 150