With addition of a 3mm stroke; interference will occur between the rear piston skirt and crankcase bolt boss at the bottom of the stroke.
The crankcase must be relieved to a minimum piston to case clearance of 2mm (.080") - care must be taken to not expose the bolt hole.
The amount of relief cut will vary with larger bore sizes and aftermarket pistons.
This procedure must be performed before final case assembly and is best performed on a bare case with all bearings removed.
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