max overbore piston from wiseco is +.080" (2mm)
I believe they do come in some .010"(.25mm) increments
You will need a machinists to measure the clearance, or somebody with micrometer and or dial bore gauge experience
Did he get it turned after that?

1. Just buy new springs from polaris, if dg used something different use theirs. another manufacture might work also. (yamaha, arctic cat)
2.the springs? I use a shoe lace or a piece of electrical wire. some use vise-grips but they are difficult in bad spots.
3. somebody on here said they don't use the support bracket on that side of the starter. I do use them though(some engineer decided they needed to be there)
yes you need a clutch puller. threads into the clutch and pushes on the crank.
4.I use belray on my chains. If I oil them at all, it either flings off attracks dirt or gets mixed with mud pretty good anyway. KEEP THEM TIGHT