I have a 48cc motor on my bike two weeks old, way past break in period. The top speed was at 30mph. I was riding it last night at full throttle off and on for about twenty minutes. During the end of that twenty minutes it started to bog down, and struggle. I rode it again today and for the first 5min it ran fine, but then bogged down again. It gets to 20mph but at full throttle, and then slows down to 16mph. The throttle will be completely down and nothing happens. It will run at 16mph will it slows down and pick back up again to 20mph, and this will repeat. When the clutch is in the throttle revs fine, but in gear it struggles. After a cool down the engine runs again fine for a few minutes then bogs down again. Any help, I don't know much at all about engines. Also if it matters at all the mix ratio has been at 16:1.