Yusa buggy?

Novak finally started giving gearing recommendations for their motors. The do not recommend using the 4.5 for anything but a speed run, but they suggest using a 10-11t pinion for the new 5.5 (depending on model). Also, assuming you are still using the 1/8 in shaft, the old 4.5 is equivalent to the new 5.5, so a 10t or 11t should work. If you have a plastic spur, century and thunder tiger make mod1 pinions for their helis (go down to 9t) but they are not hardened. I think Novak has "hardened" pinions now in 11t, maybe even 10t.