Hmmm well we got 18HP on a true reading dyno...........with the rear brake jammed on. Went to 23HP with that fixed, (owner is a mechanic too
) and jetting miles out. With some dialing in at the track it started to really haul arse. Then the piston cried 'enough' so we were looking north of 25rwhp.That's also with a shit pipe (about 200mm to short) a shit straight line (fixed curve) ignition and very conservative disc timing. With those fixed hmmm I shouldn't say but probably well over 30HP if you used a decent piston.
Dos we used (as did Nitram many moons ago when he owned the said KH125) KT100 S and J kart rods with a Thompson big end cage , nothing ever looked like failing.