| Dave,
John's suggestion is good, turning the hoses around the outer locking rings either side of the mouthpiece should help. If you are new to diving the unit give yourself time to relax, I found that early on I had jaw fatigue caused by gripping the mouthpiece too hard between my teeth. After diving OC with a negatively buoyant mouthpiece the positive buoyancy of the unit's made it feel insecure and hence the tendency to hold on a little too tight.
I hope you sort the problem and enjoy diving the unit.
Dive safe. |