I pulled the Mikuni BSR42 for the first time to tweak the jetting. The rumors are true, the carb screws (both bottom and top) are a bear to get out. My friend and I had to use a small cutter to cut a flat head slot for all screws (4 bottom and 2 top). I replaced all the screws with stainless steel, socket head cap screws. When visiting your local bolt & screw business, here's what you should ask for:

Stainless steel, socket head cap screws (allen head)

For the top
* Qty 2 - M5 x .8mm (pitch) x 8mm long

For the bottom
* Qty 1 - M4 x .7mm (pitch) x 14mm long
* Qty 3 - M4 x .7mm (pitch) x 10mm long

 

Yeah, I have re-jetted several times this summer and also rebuilt a carb. The stock screws really suck!!!!

 

Mine came off pretty easily with a set of needle nose vice grips.

 

ive had no problem with the screws but ive replaced them anyways