Ive used this caliper before for blaster, and honda 4 stroke cylinders and it gave me a right on measurement. I will have to look into the digital one. So you think this bore is stock 86mm?
Digital calipers are not any more accurate that the verniers calipers pictured, Digital calipers are just easier to read and usually need a battery every time you go to use them.
The diameter of your bore at the top of the cylinder according to your calipers is 86.1mm. Now measure the diameter of the bore 1", 2" and 3" below the point where you are currently taking the measurement in the above picture to get a accurate condition of the bore. It looks like there is a lot of rust in the bore. What is the diameter of the bore going to be when the rust is removed?