I have a 2013 ninja 300 that i got from a friend at about 23k miles. Is there anything i should be worried about maintenance wise ? The owners manual goes up to i think 20k but after that nothing... I know the usual tires, chain, oil and things like that but anything specific i should be worried about? Also it makes a jerking motion back and forth when i let the throttle out a little or am holding it steady. Is that something i should be worried about? A new rider just getting started and can use all the help i can get.