Test rode on street, ran it through the gears and it ran very well and crisp. Took it out to the trails and it ran very well. Went riding yesterday and the bike did not run great. As long as I rolled the throttle on easy it was fine, but when giving it a healthy amount of throttle it would sputter. fresh gas, plug looked fine. the only thing i changed from the previous 2 rides was a new air filter. Any thoughts? Thanks.