So, the bike in question isn't mine. Its My friends. He just got the bike from his dad, and I squeezed as much info out of him as possible. I'm the one with mechanical expirence in our group of friends who ride, so he's come to me for assistance. Heres what I've gotten from him. '04 KX250F Low compression (apparently that happened overnight...?) Idle screw stuck in. Let me elaborate. He turned it in in an attempt to raise the idle (lord knows why...) and it got stuck. Wont turn out, won't turn in. Exhaust gets bright red. That's why I said it was running lean. Apparently that happened after the idle screw incident...not sure if it just needs a carb clean, or a valve adjustment, or what. I've cleaned 2T carbs, never 4T. The bike has an FMF Megabomb and an FMF Q4. Also, this happened last year. Some sort of coolant plug popped out. What does it do?