These are xr 50 numbers but same motor pretty much for an idea

These are actual numbers from a dyna jet 168 we ran many runs so heres is what we came up with.

Stock 50cc -- 2.4hp

add just pipe and big bore kit 88cc no head -- 6.5hp

add good ported head w/cam to above 88cc kit -- 9.3hp

add 20mm carb to above 10.2hp

109cc with ported head,pipe,cam 12.7hp

step up to 139cc with 14mm stroker, 24mm carb, fully ported head with gsxr 1100 valves grinded to fit, custom ground web cam, custom made exhaust manual 4 speed with clutch, advanced timing 6 degrees, hi rev ignition, and you will get ---
22.7 hp. Now just add 2inches to the frame and 3 to the swingarm and way 200pds like me and you might be able to ride my 50 sitting on the gas tank to keep the front end down.

Don't believe me ask Ricky from RIS we built his motor but it's not as wild as mine though but still hauls BUTT
Rick
rick@jbcomputers.cc

NO TRUST ME ITS NOT FUN. Its actually really stupid rediculous, and its fun in a straight line or going in the dunes. I have the chromoly tube front end and bad ass shocks but it wat more power than you can even handle in that small thing.
But it HAULS ASS.
Rick