Scooter randomly does not start

[ulysse zb]

So I recently decided to rebuild my scooter, I installed a 50cc Athena kit, new crankshaft, 17.5 carb, 98 main jet, Tun'r air filter, and an Polini exhaust.

4 days ago, I got it running. After adjusting the carb, I drove it and don't worry, I was breaking it in.

First of all, I noticed the performance was a little bit weird... maybe I need to unrestrict my exhaust.

Started fine for the 2 first days. I drove it around a little bit, put it in my garage for the night.

Next morning, I wanted to start it. Nothing. It didn't start.
I tried with starting fluid, it started for 5 seconds, I tried to let it idle. It died again. I used starting fluid again, but instead of letting it idle, I tried to put gas, still died in 5-10 seconds.

I suspect Compression, because I checked the Spark, cleaned the carb.
And also my battery is pretty damn died, I think my stator is not in good shape.
Any one have ideas??