Mini Bike Issue

[Goddy Patt]

I was riding My mini bike to work and it started to bob down and then it started to knock and it won’t go when I give it throttle but it starts but it’s a loud knock sound anyone know what is it and what I should do to fix it if is the engine shot please help.

 

[Chargeride]

I'll say it first.
Is this a gas bike?

 

[CanNik]

How do you expect a reply when you don't even say make, model, age and so on