Hi,
I have a 14-28T 7 speed cassette freewheel on my MP4, but as Alan points out an 11 T smallest sprocket will help keep up with the motor. The problem is I can't seem to find an 11-28 or 11-32 or 11-anything that has a freewheel and is screw on. I ordered an 11-28T just recently but when it arrived it was the spine fit with no freewheel style. So that is no good.
I'm running a 34-52 front sprocket set so I can't go much better at that end.
Any suggestions?