What would cause the engine to pop through the carb at higher rpms? Idles great but at higher rpms in neutral or in gear, it sounds like a popcorn machine through the carb. How to tell if it's spark, timing or fuel related?

 

Check valve lash and do a compression test. Mine was doing that and had mushroomed the valves pretty good resulting in bad valve seal. New valves and lapping seats fixed it right up.