I have an '80 KDX 250 sitting in the shed I bought new. It's substantially similar bike to the 400 but for the engine. The 250 was considered the best of the Enduro bikes in 1980. It was a John Penton design he came up with for Kawasaki. Japanese parts but notice all the aftermarket items too. Vesco petcock etc... I hope you're tall if you buy it. The seat height is 37" and it predates modern progressive suspension so when you sit on it you're still way up in the air. Ride it hard and everything settles in and it feels great. Tool around at low speeds and you'll swear you're riding a barstool with 2 legs...
2011 Ninja 1000