hey everybody, i recently purchased a Bison and put a good bit of time into it. i spit it and replaced the clutch and other than that i have just nickel and dimed it. it ran great until a few weeks ago. i was using my box blade on the back and it started to pop back throught he carb. not sure what the problem is, plugs are clean, timing is good, points check out, oil and water both clean... any suggestions? really need to get her running again.