Phbn/phva carb setting?

Hi

Is the Dellortos phbn/phva float bowl able to set? Or is it a fixed setting on these models?

Cant find any info on this model so assuming there is none to tell.

Symptoms are a wet plug and bogging at higher speeds, just dies slowly.
Currently also going to get another exhaust as the one i have looks heavily gunked. When i took it off a thick sludgey black goo came out of the end connected to engine...

Thanks in advance

 

Too big main jet?

 

That did cross my mind as well after everything i have read. No idea what it should be thou.