they are usually restriced in the exhaust downpipes on a model like this,is it using the honda cb125 tdc engine thats a parallel twin cylinder ,it will also be restricted via the rev limiter that is built into the cdi unit but its finding out what wire to dis connect to take that out.a simple way to gain more top end is to increase the number of teeth on the front sprocket providing the bike reve out fully already in top gear?if it does then take the front sprocket up 2 teeth and see how it is a sprocket will cost you 10-15 quid
adam bike doctor(of milton keynes motorcycle centre), November 2010
