I did my big bore with 1 but alot of the low end tuneing was by feel and pipe temp. It will read leaner at low and mid rpm but you cruse down the trail in the midrange. So keep the power smooth check your plugs(if you can dependant on fuel), and around 13 would be good for afr. When i set it up this time it will be with egt's you can see more of what is going on, and afr seems to jump around more at lower throttle positions.