I find most transiotion problems are low end related. The engine runs on the low speed needle for about 2/3rds of the time. Only the last 1/3 is high speed needle. If no amount of high speed needle tweaking gets you there. And your glow plug is good. And you check for no air leaks around the carb base and the engine backplate. Try adjusting the low end needle. Any of the above can give you fits trying to get a good transition. One last question, is your fuel fresh? This also can cause fits. Good luck with it.

And to answer the Royal question, Absolutely! The older Royals were a decent and fairly powerful engine. Good luck with it.

Mark Shuman