Re: How Hard is it to modify the jet?
Larger hole more fluid the carb atomizes the mixture anyway. Done it it works! However, if you can buy an assortment of jet sizes for cheap why would you mess around w/ drilling them.
Beyond smoothing out ports and maybe an air filter, every mod will require rejetting for a truly tuned motor!
The only adjustment you get w/ most of these carbs is from 1/4-1/2 throttle by adjusting the needle. Idle circuit stays "about" the same on most motors independent of state of tune so not really missing anything there. But if you change something i.e. exhaust, air filter, port timing, compression etc and you need to adjust 1/2 to full throttle, i.e. the main jet, then you either find'em or drill'em. Cause if you don't you'll have one sticky piston!