novarossi based and sirio engines have problem as you mentioned, that's why i run OS, it fits perfect without the need for modification.
Originally Posted by kidDynomite
Just wondering if any of you are running a Sirio EvoIII in your MTX-4?
I found that the carb slide's set screw nub hit's the back-angled part of the fuel tank. I actually had to grind some of the nub and set screw at an angle, as well as, turn the carb slightly to the right so that it will clear that part of the tank, but only by about 0.5mm.