I'm rebuilding a '98 RM250 and think I might have a problem with Piston to Cylinder clearance. I had the Cylinder replated and honed by US Chrome, I sent my new Wiseco piston so they could hone it to the correct clearance. The piston box says Clearance: .0015 in. I measured ring gap at .008 and .009 in. which might be a little tight, Wiseco says .004 in for each inch of diameter (.004 X 2.61 = .010). After installing the cylinder and rotating the crank it feels smooth but I can hear a noise that sounds like the piston is making slight contact with the cylinder. I hear the sound as the piston gets close to the top of the stroke. It kind of sounds like a file on metal, I think the skirt is contacting the cylinder. I tried measuring the clearance with an outside micrometer and a telescoping gauge but I'm not too good at it, I keep getting different readings. This isn't my first rebuild but I'm no expert either. I don't remember hearing any noises like this before. This Wiseco piston has some small grooves or ridges going around the piston and I think that when the skirt makes contact I hear the filing noise. I don't remember pistons I've used on other bikes having these grooves, I think they were smooth. I took the cylinder off, cleaned and relubed everything then put it back on but get the same noise. Now what? Any ideas? Could this possibly be normal?