kx125

So the issue at hand... the "water pump comp-shaft gear" ( gear located at the back end of the impeller shaft) happened to be straight broke in half when I bought the bike. there was no located remains of it in the case, so the previous owner must've already known the problem and failed to tell...

I just rebuit my 125 and it runs perfect again but idk what to do to break it in. Should i let it idle a while in the garage while holding the rpms kinda up or would riding it a little easy for like a half an hour wor. Also im mixing 42:1 right now so should i mix richer will it a new piston...