I bought a 2007 650 H1 yesterday and after getting it to the ranch am experinsing only 30 MPH top speed and 4200 RPM's from the engine. I have checked and cleaned the air filter, checked cleaned the spark plug and drained the carb. At just over 30 mph the engine pops and sputers back through the carb. Tried going down a steep paved hill nearby and 32 is as fast as it will go without missing. What should I begin checking to get it to run better?