I have been trying to educate myself so that I can do the best job possible installing a Wiseco piston into my 04 KX250. It will be the first time I have done this, but I am not too worried about it. Have you all taken cylinder diameter measurements when doing the top end work? I was looking at cylinder bore gauges and it looks like a decent new one is ~$120 minimum. I am thinking it may not be all that necessary though because I will be able to see if the coating is looking good, and that should tell me something I think - that is if the coating is uniform and not pealing off anywhere it is probably reasonable to think the cylinder diameter is close to standard. Also, I will be able to take my new Wiseco rings, place them at different points in the cylinder and measure the ring end gap. My manual says standard ring end gap is 0.0098 - 0.0177" - and Service Limit is 0.030". If I can assume my new rings are the right size and don't need to be filed then I can get a sort of backdoor cylinder diameter measurement, thought only known within 0.007" or so. Fitting the piston and checking clearance may not be an option, but if it is feasible, then I can get another measurement that is related to cylinder diameter. I do have a good caliper, so I can measure outside diameter no problem. Have those of you that have done new top ends several times taken measurement of the cylinder diameter to see if it is within spec using a bore gauge? Do you think the above ideas will be helpful in getting a decent idea of cylinder diameter or not? Any experience you could share about this would be great. Thanks.