Chinese engine no start.

Hi, I have a problem with my new engine. It's an 80cc engine from ebay and it's chinese.
I fitted it in my bike last week and when I went out to the street to try it. During the first tests it
turned on and worked for a minutes but not worked at all. The next day I went out to try it too but
it hasn't worked this day. I have been trying to turn it on but I can't. The sparkle is ok I think and
the carb. too I supose.
What could it happen? And what could I try?
Please help me.
Thanks.

Hi, thank you Nougat! My engine bike is working perfect now!
The problem was the carb, now is on the intake solidly and works well.
I'm happy to see that there are good forums like this, thank you Fairracing31.