The Lexmotos all have clones of various old Japanese air cooled 125s, and generally with more relaxed tolerances. As a result, there isn't really much you can do to get more out of them - that's as good as it gets! In theory you could change the gearing a little, but the very limited torque doesn't really give you a lot of wiggle room there. I know it's not exactly the answer you were hoping to hear, but honestly the engines in these are already doing pretty much as much as you can hope for! We did have a forum member a ways back who kept trying to boost the performance of Chinese 125s, but he mostly just blew them up spectacularly