89.0 mm is the stock bore for the 1989 Honda cr500r.
90mm stock bore size on my 2002 foreman 450cc
78.5 MM
i believe you can go 8mm over stock bore but im not one hundred percent my machanic did mine and he said a 4 over was the best bore for one
The stock bore was 4.125". The bore of a 406 would be 4.155"
Stock bore size 64mm Max 66.5mm
Stock bore is 42mm.
The bore and stroke is---3.740 bore and 3.480 stroke. STOCK 305
it is a 281cc
bore 3.497 stroke 3.81
4.125 inches
3.736"