Hey, a  03 sporty still as the trap door for the trans, which is a plus!! your scoot is 520 lbs dry and you say the chair and passenger are more than that?!? wow!

A 1250 kit with some head work and some N4 cams would give you an increase of close to 50% more HP and TQ which is nothing to sneeze at! Probably looking at $1900 if you do the work yourself.

The wheels are 19" front and 16" rear with 3/4" bearings, you can fit 110 tire up front at the biggest, the rear is a little diff. tho so them rims might not fit, changing the front tire from a 19 to 16 will change the tracking plane, you might have to do some adjustment with the fork tubes in the triple tree. All things you have to calculate within your total cost!

If you want an idea of how good a 1250kit really is....I have over a 145K on mine with no issues except burning rubber if I'm a little to aggressive on the throttle :)

Thane Gillies wrote:

Horse power is very much related to RPMs. Higher RPMs give higher HP ratings . Sometimes a cam that gives more HP does so at the loss of low and mid range torque which is more essential to sidecar work. Bigger displacement sometimes works better with stock cams than "high HP" cams. 

That is true, but N4's are an all around set of cams, they are a bolt in, not too much lift and a bit longer duration with a good LSA....work best with a set of ported heads which is best with a 1250 kit, a good squish band, a comp ratio 10/1 no more ....I've done many of them with that configuration. The stock W cams don't work well with an increase in comp.

The closing event of the N4 is just slightly later than the stock W's, the N4 really wake up the mid range and top end without really changing the bottom(very very subtle change)

They are better than Screaming Chicken 497 cams for bottom end.