I have a 12 300 xc. I recommend that you use the jetting guide in the back of the users manual.. I have found these settings to be fairly rich so I usually move 1 box leaner to start.. Also if you want that bike to really run send the head to Slavens and have him do his thing, then request his gasket, and install everything.. The cylinder is already decked on the 12, so all you need is the head work and gasket. Either way you need to send the head out as this will make the engine much more responsive to jet changes..