A forum for owners of Yamaha TTR250 trail and enduro bikes!

By factory settings do you mean jets and emulsifier sizes, needle position, or fuel screw adjustment? Needle position is normally in the middle slot. Fuel screw 1.5 to 2.5 turns out depending on how the bike runs when you're setting it up, but I find it makes very little audible difference. Jets and nozzle depend on the year and market of the bike in question and there's a lot of info here
ttr250.activeboard.com/t49703293/carburettor-main-nozzle-differences/
I would suggest that if the exhaust you have fitted in the picture is more free flowing than the Yam one (highly likely!) you will need larger jets than standard anyway,to avoid lean running.
For float height settings try this thread:
ttr250.activeboard.com/t57547519/adjusting-the-fuel-level-in-the-carb-bowl-float-height/
Have fun!!