Thanks so much for the pics. I truly appreciate your help. As it turns out, my carb, RB-K66b, is non-adjustable as it has a fixed jet and is different from the one in your pics. This I learned from discussions with a Zama engineer..
After explaining the problem to him, he said he was certain it was a restriction causing the non-acceleration issue. He went on to explain how to clean the jets for both the high and low circuits which he gave about a 50% chance of fixing the problem, and if it didn't cure it, a new carb was about the only solution, he added.
I asked about an adjustable carb replacement, and after a little research, he suggested the RB K75, a direct bolt on which would also provide a little more power. They're on Ebay new for about $45 with shipping.
If you refer to the carb schematic I provide above, the fixed jet is no. 18, and 21 and 30 being the plug and its o-ring. On some Zama carbs, this is where the high adjustment is. On my carb, the primer base, no. 12, must be removed to access the plug which merely slips out after base removal. As I quickly found out when trying to adjust my carb, the engine will not run with the plug removed.
If anyone has any questions regarding any info here, please let me know. And thanks again XPLRN. firstname.lastname@example.org
I'll update my progress.