KTM 390 Duke has a bad ❗spark plug cylinder head problem❗, here’s what that likely means and how to fix it 👇 Thank you Boss. AR Superbikes 😊 🔍 Possible Problems 1. Spark plug threads damaged (stripped) The aluminum cylinder head threads can easily get damaged if the spark plug was over-tightened or cross-threaded. You may notice the spark plug not tightening properly or blowing out when the engine runs. 2. Spark plug hole cracked or burnt Overheating or detonation can cause cracking around th