So I've got a ciao and a bravo doing the exact same thing:
It starts fine, no problems. But then when you drop it off the stand, it kills. It's not the idle or anything, it's like the engine instantly dies. Like it loses spark or something? You can pedal it off the ground and get it going, and it runs great, but sometimes when you stop it just cuts out.
The spark is good, and both electrical wiring seems to be in good condition.
This is so vague, but it's all I got! I've never seen this before, but now 2 of my bikes are doing it. Is this a condenser problem? That's the best I can come up with.