Motorcycle Repair: Motox bike engine query

Question
Hello I am rebuilding my 1998 Honda CR250 engine  ,I have purchased a complete rebuild kit with a B size piston to accommodate the cylinder wear , I'd like to know the minimum piston to cylinder clearance possible

Answer
Shane, The piston std size is about 66.35mm the A,B,C, mean about .001 increase. Example B wpould be 66.36 and C is about 66.37mm. Measure the cylinder bore front to back about mid way down to get the most accurate measurement. Also measure the piston skirt as the piston is slightly tapered to expand on the top and fit. Also factory specs for clearance is .06-.07mm or about .002 thousands to two and a half thousands at the piston skirt. Use a feeler gauge and place it in between the piston and the cylinder wall it should have some drag pulling out the .002 blade. Because of the nikosil coating on the cylinder wall its tough to even hone a crisscross pattern.