I have some vertical scoring on the R.H. cylinder wall on a CB450 K2 engine that can be seen by peering through the plug hole. Compression is down at 135psi (hot) on both sides, though a teaspoon of oil gets this up to 185psi. My thought is to take the barrels off to take a look what's going on. My gut feeling is it will need a rebore and pistons. If this is the case, does anyone know what the quality is like of the David Silver 'replica' aftermarket items? OEM works out fairly expensive.