I'm not so sure about the weight thing. I weighed 207 when I bought my TBA and this was right after a kidney transplant. I have gained 80lbs plus in 4 years (enjoying the good life too much) and I got around 40mpg then and the same now combined city and highway. I have only taken 2 baffles out of the pipes, and the air injection removed. If you figure the gross weight limit, according to the manual, is supposed to be 400lbs, it shouldn't make that much difference unless you are over 400lbs and then carry a passenger and luggage.
I would also think the 18 and 19 tooth sprocket would get better mileage??
