You can't it's a 4 stroke, get a bigger bike!
Seriously you can't other than spending a load of cash to turn it into (I think) a 180cc (new barrel, piston etc & new carb), waste of time (and money)
If your resticted to 125cc (as I am and I'm 44!) get a 2 stroke, pull the washers out of the exhaust and go screaming round like a tw*t!
tHE MZ 125 a great bike with a modern engine(i've got a melon Yellow SX) I've even used one off-road but way to heavy and underpowered but a way cool street bike and jeez it'll do 65MPH.
Whaderyerwant?
Comments please?..............................
Str.
p.s. fit nitrous?!
My Bike;