I uploaded some info (plus one photo) to the topic "Technical | How To" on up-gearing a Kymco 50cc 4T. Gears are relatively easy to install, but you need to visit the transmission shop or a motorcycle machine shop to press one set of gears together. Kymco 4-strokes use mostly Chinese gear sets, and the upgrade is not expensive, but there can be little quirks as described in my post. The speed increase is well worth it!