Hello, I have a 2004 trailblazer, 250 cc eng, that i have toasted a piston on. I have the jug off and piston in hand. Can anyone tell me what the spec is for the standard bore of this engine? It measures at approx 2.829. I need to order a piston and will go as large as i have to. Just don't know if it has ever been bored before and don't have a manual. Thanks in advance!!!

 

Stock bore --> 2.835"

20 over -------> 2.854"

 

take your cylinder and piston to a dealer that bores cylinders (a lot sub out to machinists!) He should be able to tell you what oversize to bore that will clean out cylinder usually second over will clean up unless deeply grooved. After bore and hone,with piston in cylinder without rings, check clearance, should be no more than .0015-.002 with feeler gage. Ring end gap .008-012,can file ring ends if dealer doesnt. BREAK-IN slowly.