Hey guys. I noticed that my bike has recently lost a significant amount of power in the last 3 days. I can only reach up to 23mph top speed and before I could get it up to around 33. Also I lost the cap to my muffler which makes it extremely loud and after about 20 mins of riding, parts of the muffler turn red hot and when I rev the engine high the muffler blows flames sometimes. My mpg is also low, like 40 miles per gallon to the gallon.. 20 miles per tank.. what the **** is wrong?