Low-idle stalling when pulling in the clutch
Early Ninja 300s are known to stall when the rider pulls in the clutch or rolls to a stop; NHTSA logged a cluster of complaints on the 2013 model. Kawasaki addressed most bikes with a free ECU reflash. On the test ride, let it warm up and pull the clutch in at speed — if the idle dips below 1,000 rpm and it dies, the update was likely never done. Ask for dealer records showing the reflash.
Ask for repair records covering this item. If it hasn't been addressed and the car is in or near the mileage window, price the up to $250 repair into your offer — or make it the seller's problem.