Cub Cadet 2135 won't start
Kohler 13hp in a Cub Cadet 2135 Yard Tractor. New: carb, oil(and filter), spark plug. Cleaned and lubed. Ran great the first mowing after maintenance, about halfway through the second mowing, started chugging and vibrating oddly(an odd sound, almost like a loose hood or side cover, but not exactly), PTO off, calmed down, leveled mower, PTO back on, same thing. Tried letting cool for about 15 minutes, started fine, PTO on, same thing. Let sit for 30 minutes, now won't start at all, not even an attempt to fire. Has spark(though it seems to be a constant white spark), checked compression(is good), and looked at valves(moving fine). Thinking ignition module, any other ideas?