GY6 vacuum leak

[Freddy]

Hi guys,

I'm new here, just scrolled around to see if there are more people with my problem. Decided to start a thread on my own. Hope someone can give me a good advice how to solve it.

So, my recently purchased GY6 scooter produced a LOT of smoke from the exhaust (that's why it was cheap). I changed the piston rings and the entire head. Cilinder and piston were a bit worn. Some stripes at the cilinder and the piston was stuck, didn't get it off. Former owner probably has driven without oil.

Anyway it rode fine, although a big main jet (Keihin 19mm - 88 jet) and quite high idle. Now after replacing it doesn't anymore. After 30 seconds of trying it started. After this it almost started instantly and then slowly stalls (smoke is gone though). And then doesn't want to start anymore for a while. It also stalled while trying to rev. Changed the jet for a smaller one and played with the stationary screw but in the end it stalled anyway. I found out that there is no vacuum. When I kickstart there is no gas flowing. Sucking the petcock vacuum line gets it flowing.

There seems to be some small cracks in the intake manifold. Going to replace this. Maybe I damaged it while removing. Floater cover gasket also needs to be replaced. But maybe someone here has some brilliant advice of other places to check for vacuum leaks apart from the vacuum hoses or the intake manifold. I have no experience with this vacuum system, so not 100 percent sure how it works. Spark plug, exhaust, head or foot gaskets? Pressure problem? Maybe some of you have experienced kind of the same, on a GY6 engine?


Edit: I've put my carb in an ultrasonal cleaner for an hour, so guess the carb is clean from the inside.