So this morning I noticed a problem with my 250. Whenever I would reach 9k RPM or so, the engine started bogging (almost like a consistent start and stop motion). At this point, I could barely accelerate any further even at WOT. It works fine under the 9k RPM mark though. What can this be? I have a 100% stock 2009 Ninja 250 with just under 10k miles.