Once or twice over the years, when I've had a carb apart for cleaning, the float stuck open when first used. No idea why. On those occasions, I've just tapped the float bowls lightly with the handle of a hammer, and the problem disappeared, never to occur again.
Probably my own clumsy reassembly, but I'd give it a try, anyway.
Seems unlikely that the shop would've done this work, and not tried it out themselves. Something catastrophic like an upside part or misadjusted level would have shown up for them just as quickly as it did for you.
Good luck with it,
Kirk
*edit* oops, just re-read your post - not sure if you sent the whole bike, or just the carbs themselves. Hmmm... I'd still give the tapping thing a try.
K.
Poll