Hey J,
Both carburetors work great on the 125RÌs. You donÌt have to worry about the manifolds, because both carbs are from the same body. So the OD that fits into the manifold is the same. The only thing is the 32mm is 102mm from front to back, and the 34mm is 93mm front to back, and the stocker is 93mm as well. But IÌve use both carbs on bikes IÌve built for customers, the only thing is if you use the 34mm you might want to do some work on the head to give the bike a little more bottom end, do to the fact that youÌll loose some of that stepping up to a larger carb. If you go for the 32mm you wonÌt have to do anything really, unless you want to shave down the bell to 93mm which will increase the bottom a little. Hope this helps.
