Don't mess with the transfers at all. The angles in the transfers should not be disturbed and they already flow much more than you can use. Raise the exhaust port window about 1 mm and square it out than funnel port the exit to fit your pipe. 25mm exhaust is about the largest you will fit to the existing studs in the exhaust port of the cylinder. This should get you blasting close to 50 mph on the flat and is pretty close to your rev limiter in the cdi which should allow you to reach about 52 to 53 mph reaching about 10,500 rpm. A simple bullet pipe shortened 3 to 4 inches will work well. Biturbo will also work will shortened. And this is done with the stock carb. Low mid and high speed is greatly enhanced and with the stock air box as well. I have a 2007 revival that blasts and rips to 50 mph all day long and has 20,000 miles plus using 26x22 drive sprockets.