yz 125 jetting

I am still learning about jetting myself, but would recommend eric gorrs website and do a search around here. There are so many factors that appear to affect your jetting such as the weather, altitude, fuel, oil etc. I would start by finding out what jets, needle etc you currently have in the bike, ie are they stock.

What is the bike doing that makes it feel rich?

Yes, go to Eric's sight and read his jetting guide. I've posted that link enough lately, do a search in this forum for jetting, and you will find it. It's really impossible to just tell somebody what jets they need. Like merlinnn pointed out, there are so many factors that effect jetting... READ THE GUIDE ;)