Can you put ttr 125 carburetor on blaster 250?

First, a Blaster is a 200. As for the carb fitting, though it may, I'd highly recommend that you find an alternative. That particular carb is restrictive for the 125 4 stroke; it would wreak havoc on the Blaster's powerband. You would see a substantial loss in power. Any carburetor 26mm or lrger would be fine with the Blaster, but make sure you jet it correctly. This doesn't mean to buy a stage 3 jet kit and put it in and ride, unless you want to melt your piston.