Re: bike is way slow, any ideas?
One big difference might be that your friend's bike engine is broken in and yours is not. These little engines run better and better the more miles they accrue.
Also are the rear sprockets the same size (tooth count). Rider weight? Tire size?
There are many variables to consider when comparing performance. In addition it is a known fact that some engines just simply run better, produce more power, than others. Maybe your friend got a good one.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"