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Motorcycle Repair/Motox bike engine query


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

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.  

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Gary Blake


I have built from ground up race winning motocross bikes and atvs as well as atv,s for flat track and TT racing. I am starting to take on the utv challenges now for racing. This is a new area for me so Im in a learning curve.


I have extensive experience in off road motorcycles and atv,s.I also work on street bikes and personal watercraft, Some experience was self taught and some was factory trained. I have been working in the powersports industry since the mid 70,s I hope I can help. Thanks Gary

Was a sponsor for K.O.R.R.(kansas off road riders) and now I am working with ROMEO,s (retired old motorcyclists eating out)and was in charge of the Quad Wars for the monster truck series in Central Kansas

Factory trained Kawasaki Heavy Industries. Factory trained GasGas motorcycles and atvs worked as a technician and was as a dealership owner.Kaw.Suz,Honda,Aprilia,Arctic cat,See Doo,Can Am, Bombardier,Yamaha,GasGas,Qingi,TM,Moto Guzzi,Harley,s

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