My Model B had a surging problem until I found out that there was supposed to be an "anti-surge" spring on the governor linkage just in front of where the linkage hooks to the throttle lever. I found a little hole in the linkage. Looking in the parts catalog, I found a sping is supposed to hook there. It is the anti-surge spring. The AGCO dealer wanted $14.00 for the spring. I went to the hardware store and found a spring that is about 1/4 inch in diameter and about 2 1/2 - 3 inches long and of small gauge wire. It has hooks at both ends. I hooked one end in the little hole on the linkage and the other end to a maniforld stud and it works great. Cost = $.70. Just be sure you have the spring hooked to one of the front studs. I found out that it is not a throttle return spring, so it should not be hooked up to pull the throttle closed. It should put mild resistance on the linkage as it opens to prevent the throttle fron surging.