I've seen a set on Parts for scooters as well as Ali Babba. They are three spoke alloy that come in 3-4 colors, and cost 99.00 US. The issue is they are 2" wide so any tire you use has to be tiny. Your wheels may weigh 2-3lbs more but that's about it. I'd look into a stuffer crank, and inner rotor Ign before wheels. You could easily loose 7-8 lbs inside the engine, and get instant throttle response. 4-5 hundred I imagine. I'm pricing an Ign for the QMB 139 as we speak. I emailed HPI about my few remaining issues w/ the ZX set, and asked about a second rotor kit minus the cdi. Timing can be modified at the stator on the 4t. No need for fancy curves. It can even be set to fire at every stroke to maximize power, and efficiency. Just the rotor kit is around 3 bills. The crank maybe 150-200.00
More sh** to ponder eh!