I probably have about 30-40 miles on my bike so far, and have been using a 20:1 gas to oil fuel ratio with non-synthetic 2 stroke oil, I don't know if it is meant for air cooled engines or not but... don't know if that matters but I'm sure it helps. Anyways, I wanted to know how do I know if my engine is broken in yet, I am almost done with a gallon of gas and I am wondering what fuel mixture to use when I refill my next gallon at the gas station. Also, my max speed so far is about 23 to maybe 24 mph full throttle, but I don't hold WOT for a while because I heard it's bad... I'm sure I would accelerate a little more if I held it at WOT. But will my max speed increase naturally overtime when I switch fuel ratios after break in? Also, I plan on getting some high performance parts, but what does an expansion chamber muffler do? Make you go faster?