Now that the Yamaha YFZ has been successfully pounded by many ATV enthusiasts across the country, we are starting to see the week points in the original YFZ design. One of which being the amount of oiling the wrist pin and upper connecting rod are receiving. We have seen many cases in which the upper wrist pin is scoring inside the connecting rod from lack of oil and in some instances causing wrist pin seizures.
To correct this problem Janssen Motorsports is offering a case modification that drastically increases the amount of oil being applied to the upper connecting rod. We highly recommend this modification for all YFZ owners regardless of engine modifications.