My keeway superlight 125cc I have fitted a 150cc

SOURCE: piston rings

First, be sure they actually do fit the bore. Take a ring and insert it in the bore. push the ring halfway into the bore using the piston. There should be about a 1/32" gap in the ring. Anything more than 1/16" and you need rings the next size up. If the ring won't go into the cylinder because the gap fully closes, the rings need to be a smaller size.

With the correct size rings, put them on the piston. Some pistons have an index pin in the ring groove Fit the gap to the pin. Put the piston mid-stroke and place the cylinder over the top of the piston. Squeeze the rings closed as you gently tap the cylinder downward and over the rings.

Please rate this solution. Thanks garethholleb!

SOURCE: keeway superlight 125 adjusments

Pull the slide out of the carb then move the clip on the jet needle down one or two notches. This will richen the low range fuel mix. You can also get a rear sprocket with about 4 more teeth. This will get you off the line and out of the corners faster BUT it will also lower your top speed.

Please rate this solution. Thanks supergunner!

SOURCE: carb tune up gilera runner 50

on the carb you will find 2 screw one will be quite far in than the over thats the one you adjust this is the mixture screw which controlles the air and petrol together unscrew it say 1/4 a turns at a time and see if it improves if it gets worse screw it the oposite way and see if that improves good luck buddy

SOURCE: 2 broken side panels for keeway superlight 125

Go to: http://keewaysuperlight.blogspot.com/ and you will see how to repair your Keeway Superlight panels with pictures and instructions.

SOURCE: I want to know how big i can bore out my 125cc 4

I believe the pistons only range from stock to 1st oversize. Boring to first oversize will not make a noticeable change in performance. If you want a real change what you need is a race cam. You will be able to wax any other 125cc and many 150cc bikes. Below is a source.
www.webcamshafts.com