The original standard needle jet for the 16H was a 106.5. It makes a huge difference if you change from a carb set up for that. However if the carb has been optimised for a 106 you will have the same problem if you change back.
As I couldn't initially get hold of a 106.5 I used a 106 and had to raise the needle and go to a 190 main jet to compensate. I originally had to change the needle jet as it had worn oval and I couldn't return it to exactly the same axis.
I run a 19 engine sprocket in place of the standard 17 and the engine happily pulls that with a 45mph cruising speed and a top speed over 60.
Pre monoblocs don't tune like monoblocs/concentrics. Having experience with the latter I'd never found that changing the main jet could compensate for a different sized needle jet. Talking about this to a very old TT racer he opined that premonoblocs were indeed 'tricky'.