I would recommend the F80 for your weight requirements. These kits work better on mountain bikes but have been successfully put on 10 speed road bikes. I would recommend getting the widest tire you can put on the bike, thin tires burn out fast when you have torque and have less traction and allow less leaning in turns. As for reliability? I will say that these little bikes can become reliable, that is, after you have gotten all the kinks out, but be prepared for some difficulty until then. Carry some basic tools with you for the first 200 miles or you might find yourself peddling it home. Also, these engines create quite a bit of vibration that has a tendency to loosen screws so be prepared to tighten and tighten and re tighten everything on your bike. however over time you may find that it is just a few certain ones that come loose. Since you asked about upgrades I would recommend a sprocket adapter instead of the rag joint set up for the rear sprocket. It will drive the hub instead of the spokes and might save you much frustration. Also, a high compression head with large cooling fins will not only give you better compression and more power but keep the temperature of your engine down for more reliability. Also, ride her easy, disengage her and glide down hills, don't let her get too hot and let her cool often, use a high quality semi-synthetic 2 stroke oil properly mixed (no thicker than 24x1), treat your china girl good and she love you long time.