Same basic engine as the Rincon. Not a big fan of the 3speed but at least the pioneer has lower gearing than the Rincon.
I haven't had to work on a Pioneer, but I've rebuilt a Rincon engine. Wasn't something I want to do again, but I will say it's been a tough machine. My buddy sank it a half dozen times and likes to hit the rev limiter and even with all that abuse it just recently started smoking.
I tore it down, cleaned out the bottom end, had it bored .25 over and replaced the cam chain, oil pump chain, and oil pump orings and he's back to rooster tails. I did put the secondary out of the SxS into his machine to get the gearing lower. He can wheelie it now with ease, although it did cut down on his top end a bit.