I agree with T.O.M. Mine swings the 23X8 fine. Also, the plug that came with mine was "junk". When I pulled it out of the bag the center electrode was almost touching on one side with a big gap on the other. I didn't have a CM-6 on hand so I tried to break it in with the stocker. It did run but not too good so I went and bought a couple of new CM-6's and put one in and it ran much better. We've had a number of folks at our field have bad experiences with the stock plug although one gentleman had a good one so I think it's "hit or miss" like w8ye said above.