I've also been working on a Vespa Bravo in recent weeks. As a brief history: It wasn't starting. We checked for fuel, spark, both which it had. Figured it was compression. When pedaling, if someone puts their hand in front of the head you can feel a strong breeze. If you stick your finger in the spark plug hole and pedal, the air does no force your finger out. Also, the last plate on the head is broken. BUT: We took off the head, cleaned the inside, retightened everything, and also reset the clutch cable, which know moves much easier than it did before. Once it all went back together it started right up.
When cold, it starts right up. After a five/ten minute ride, it doesn't want to start again. Sometimes after being riden it'll start, run for a couple minutes and then die. Then it won't start at all, but if i let it cool down, it's more likely to start. Also, last night i got frustrated, kept pedaling and then this huge pop sound exploded from the back. i'm a little nervous about that.
Anyway, any ideas about this? My first inclination is to clean the carb, which i haven't done beacause I'm uncertain about how to get it out. So my other question is to those with a bravo: how do I get the carb out? And then there's the main question, which is: what's going on with this bike. any ideas?