After adjusting the valve clearance on my xflow It has started burning Oil. I removed the spark plugs, and found the plugs on cylinder 3 & 4 were covered with oil. The valve clearance were quite tight I reset them to manu spec. could it be burnt valves?

cant see that causing the problem,when does it smoke?

Piston/ piston ring problem or valve guide problem.

Because of the top heavy piston design Xflo's tend to suffer more than most from bore wear if revved to any great extent.