When taking off the cylinder head I noticed the plug between the cam right in the middle of the head. I first tough I had to loosen it. After checking in the manual there was nothing on this plug. I checked on the yamaha site and found this info, part # 90340-12112-00 PLUG, STRAIGHT SCREW . I already started to loosen it, just a bit. I retighten it to about 30 ft/lbs. What would be the proper torque ? What is this plug for ? Is this plug part of the coolant system ? Can this plug be unscrewed without damaging the head ? Do I have to completely take it off to reapply some sort of sealant ?