SXR Carb Boring

[rocknice2]

I was reading on GroupK site that they recommend the carb be bored to a true 40mm.
Do they just take out the step @ the venturi. Is it actually bored or do they do it with a porting tool. I'm assuming that the entire step is removed taking care not to touch the bomb sight.
Anyone had this mod done?
I have my own CNC machine shop so I could do it just not sure what is actually done. Probably be easier to remove the step manually with a carbide deburr tool.

 

[kevbo]

I-body carbs have very large venturis relative to their throttle plate area. Install some free flowing flame arrestors and see where the main jets end up. Cutting out the venturis could make the main circuit numb when tuning and sensitive to air density.