You don't have to remove the rocker shaft to change a lifter. Loosen the adjustment lock nut and remove the push rod, The side cover on the motor has to be removed to access the lifter. There is a tool made for removing the lifter, you can probably rent from a parts store. Soak them good with some carb cleaner. The lifters sometimes are kind of tough to remove, as they tend to get mushroomed on the bottom.
