Ok, I have an 04 660. I put a 10.75 piston in it, stage one cam, .5 inch carb spacer, and no airbox with k&n. I had to split the case and replace second gear. Now I have oil draining from my tank to the crankcase over nite and it will not return it fast enough to the tank when its running. I made sure the oil tank filter is clean, oil pump is new, oil pick up in motor is clear and the ballcheck assembly is completely new. I've took the engine apart and checked it out again. Still does same thing after putting it back together. When running I can pull the return line to tank off and see the oil dribble out but if I put my thumb over it I can stop the flow no problem like there is a internal leak. Anybody that can help , please do. I need this running by the end of the month. I did change out the left half of the crankcase due to the case saver mounts were broke off. There was a seal missing behind the bearing that is at the breather outlet of case, I put it in when I did the case but could there maybe something else I might have missed? I'm stumped and have been studying the motor blow ups in the manual. But this was my first first case split.