Serious knocking sound and scraping noise

So I was riding my 80cc motor bike into work this morning and about halfway it started vibrating worse and worse with a slight knocking. Also a kind of scraping noise. eventually I had to shut the engine off and pedal the rest of the way. When it was still running it really started to knock hard and loud and seemd to not have any power when giving it throttle almost like something was engaging correctly. I haven't been able to look at the anything yet since I am at work but thought I would ask you people to see if there is a particular place I should start. Any IDeas? Please help///

If you mean to say that the mtor mounts are loose then that's not it. They are very tight and sturdy. The knocking is coming from inside somewhere. not sure if its coming from the gears or top end or bottom end. Havent looked yet,