I just bought my first 4 stroke morocross bike, a 2006 YZ450F. I did not notice it when I test rode it but after getting it home I noticed that when I blip the throttle, sometimes it pops a little and a little flame shoots out the exhaust. Is that normal or do I need to adjust something in the carb? I was told it is all stock so I believe the pilot and main are stock. The bike probably only has 5 hours on it. I am about 500ft elevation and temps in the 50s. Thanks in advance for whatever advice you can offer.