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Max HP Stage6 Sport 70cc

how you mean tuned? how can you tune a cylinder? I know how to tune a standard cylinder but already tuned racing cylinders ??.... please explain if you know ...

You can tune a cylinder for it's particular application and rider weight by changing directions of ports, changing/checking the TA/durations, changing the dome configuration,rod length, and then exhaust design.
 
You can tune a cylinder for it's particular application and rider weight by changing directions of ports, changing/checking the TA/durations, changing the dome configuration,rod length, and then exhaust design.

Now explain more or I'll open new thread for this... and go there and explain what you just say understandable. xD