When it's flown correctly, you cannot consistently beat the K4 with any other plane, except for some of the Russian planes (LA-7 and Yak-3) and even then only under 5,000ft. It's truly the best 1v1 aircraft there is at altitudes under 25,000ft.
Knowing this, you simply have to capitalize on the mistakes the K4 pilot makes. If he makes none, simply extend and try to reenter the fight after you've gained an advantage.