You would think jetting up is easier than swapping heads just to see if the engine builder has a clue??
Somewhere along the line in these many threads the carb change has been suggested , a few times , but the OP is STUCK ON FACTORY STOCK and poo poo'd a carb change , or the carb , being the problem.
I'm pretty sure carburetors are more mysterious today than fuel injection was us 30 years ago.
