Hi everybody, I just bought an new cylinder big bore kit from Cylinder Works for my Yamaha WR450F 2008 and have some doubts about ring positioning on the piston cause I've found different and contradicting instructions out there I want to clarify and discuss with you... To begin with this Big Bore come with an Vertex piston with only one top ring, beside the group of the typical spacer with two side rails and the original Yamaha piston uses two top rings and most of the instructions from piston manufacturers out there are referring to pistons with two top rings. Here I have compiled some instructions to have it more graphical: Yamaha WR450F: As shown, they avoid the wrist pin axis and also the "longitudinal" axis as well, positioning the second ring at 180º from the first Wiseco: I suppose that by "Piston Pin Center Line" they mean the longitudinal axis (because of the Engine Front arrow), I so they prefere to put the top ring pointing to the intake and the second to the exhaust, the next oil rail only a few degrees apart, spacer at 120º and next rail also at 120º Duncan Racing: I don't like this "flavor" at all, first and second gap are too close together... The scrapers are positioned at least 20mm apart from the expander gap. Now some instructions I found for one compression ring pistons: Vertex: I like this positioning, first ring pointing to the intake just in the longitudinal axis, and the spacer just opposite at 180º, with it's side rails 25º of it's gap. Honda CRF450R: I think I like these most if they didn't position the first gap just pointing to the exhaust were most of the heat will be, but positioning the first side rail just at 180º from the compression ring gap seems logical to me, and then the spacer at 90º and the lower rail at 90º again being in line with the top ring gap. Well, being the piston actually a Vertex I should simply use they instructions and starting this post may be stupid but I like to investigate things and understand why so many different flavors exist. This fact says me it cannot be that important or critical, I just want to know what other people thing and do. Some fundamental questions: - It the gap direction important (exhaust, intake, wrist pin...) or are the degrees the only real thing ? - Will the rings actually move if the motor is running ? - If they move, will they do it all the time or only during break-in ? Because I actually cannot understand why it is so important to break in correctly the rings so that they "match" the cylinder surface and seal well if the rings constantly are moving to a different mating surface area in the bore... Maybe it's more a thing of the ring taper than the actual bore wall ? Thanks for reading this far and more thanks if you contribute the the thread. Regards !