I have an 2004 crf70 that I just can not get to stop smoking. So far I have had an engine shop replace the valve seals and clean up the valves, bored the jug 1mm oversize, installed a new piston and rings, and put back together with new gaskets and o-rings. This thing still smokes like before I started. When it was apart, we checked the head and jug for cracks and could not find anything. Twice when I pulled it apart, the cylinder walls and piston were covered with oil. I am stumped. Where is all the oil coming from???????? Is it possible there is a crack somewhere that is not visible?? I made sure to put the ring gaps spaced out and followed the manual for reassembly. Compression check right after the rebore was at 120 psi. I assume this will get better with some break in time. What else can I check???????????