I've used the jet kit from Dr. Jeykle of the Yahoo Sherpa group and my 2001 Sherpa will do an honest top speed of 79 mph indicated on my GPS. Comfortable cruise speed with stock gearing is 50 to 60 mph. I am 6' 3" and weigh 210 lbs. The highest mpg i've gotten was 84.3, but that was running along on a river road at an average speed of 35 mph. I consistently get in the 65-70 mpg range. The bike is a hoot to drive, and has taught me that a smaller cc bike can be a great tool.
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