Harry - Over the past 15 years on this board, I've not been able to get anyone nailed down on jetting either the TM33 or TM28 carbs. Seems somewhat of a black art and no one is especially transparent about their R&D. That's not to say it can't or hasn't been done. As for jets and parts SUDCO
has all this stuff. Perhaps someone there can guide you regarding the TM28, XT225 and jetting.
I do know from working with the TM33-8012, its stock throttle cable bracket will hit the frame rail on the bike. So there were some physical mods required before any jetting issues were addressed. Good luck!