ttr125 - mikuni VM24 upgrade
The factory carb on the TTR125 is shit. The pilot jet is microscopic and clogs anytime the bikes sits for more than a week. At high RPMs the thing breaks up and loses power.
A common upgrade is to swap in a Mikuni VM24 carb. I made the change and, while I still have some tuning to do, the bike is running better. It has more power up top and it starts substantially easier. I can't comment on the jets clogging yet.
When running at higher elevations (e.g. 10k feet) it doesn't idle well. I suspect it is too rich. I have some more tuning to do to address that. That is about the elevation of all the interesting trails out here.