check for airleaks by running it at the lowest possible rpm you can get it to (as close to idle as you can) and the spraying around suspect areas with carb cleaner. if it goes snotty and dies then you found the leak!
when i drilled out 14.12 to 14.14 and installed it was idling high and lean. i checked around the intake by spraying brake cleaner. when i hit where the carb clamped to the intake the bike would die!! used a new plastic piece and bam it idled perfect.
on the SHA carbs you NEED to make sure the idle passage is clear tho, its a TINY passage at the bottom of the throttle slide that is aligned to the emulsion tube passages. if thats not clear, it will not idle.