taco eater :
Robert Smiley from Fountain Valley, CA United States
I purchased this to achieve piston-skirt-to-case clearance on Derbi Piston-Port casings. It's just the skirt that contacts the case on the bottom of the stroke. Since the piston diameter is basically 47mm, and the cylinder fits OK, this 50mm boring tool is perfect! The only modification necessary is to bore the "4 hole", 48mm spread setup out with an "X" alphabet drill. You also need to use 4ea. 125mm X 7mm studs and your 7mm nuts. The instructions have you putting the boring bar into a vice and inserting the connecting rod into the boring bar center WITH THE ENGINE UPSIDE DOWN using the engine weight to do the job! I found this unacceptable and do it disassembled upright, powering the setup with an electric drill. The results doing it this way are professional.
Seriously Professional Tool 
