Really I dont know if this should go in repair or performance because it could be used for both.
I recently opened up the intake window on my vespa case and wasn't paying as close attention as I should have been so I filed it close to the edges of the sealing surface. While trying to come up with a good idea on how ot fix this potential problem it dawned on me that I could possibly mill out the entire sealing surface and have a plug machined to fit.
Then it occured to me that if that was possible you could overbore the intake and fit a larger carb and passably by using shims on the outside of the case adjust the clearance between the sealing surface and the crank.
( I don't know how the crank to case clearances vary engine to engine but if it's like my intake hole being way off center this could help a lot with blow back.)
really for me atm this is just a pipe dream because i have no experience with CAD or machining. But i thought it was a interesting idea that is maybe worth persuing by people with the skills to make it work.
I hope i wasn't too vague or confusing on trying to convey my idea.
If this idea takes off and makes a million dollars I want a cut. LOL