i dont know about cutting it open and fitting it back, the only thing i can think of is replace the fire trap. you can still buy them, that would stop the oil build up, another thing you could do is remove and clean out the breather pipe from the pump you will need a new seal when refitting. the only thing i can think of it spraying oil is the veins in the oil system may be a build up on them making the pressure build up on the crank, as there is a bit of air pressure build up from the pistons, it would add more pressure if the veins were blocked, and flushing out the cam cover system, vapor chamber you would need to take this off and tip it out to get the oil etc out. you cannot really go around cutting and drilling holes as this would damage the system all it takes is a part to fail not in the normal way and cause more problems, even a peace of plastic coming off and being sucked into the engine can do alot of damage. I just did a system clean with some seafoam cleaner i had been watching videos on it and looked impressive, so tried it myself and its worked really well, it cleaned the pistons and chamber nearly back to new, you can put some in the oil and run for 100 miles then do an oil change and i did that, checked results with an endoscope, engine has more power than it did before and alot quieter than it was. and last thing you do with it is put some in the fuel you have to work out the right amounts to use for the oil and the fuel but for the breather line feed with it you can use as much as you think you need, there is other stuff but I thought i would use that. on video it say to use the brake air feed but that cannot be done on this engine as it plactic crimped, so used the large breather from the cam cover and then the small one next to it and left it to soak for around 20 min says 10 but i was having a drink, and a chat on the phone, oil change went well after, no build up in pipes and it had converted all the build up so it would be removed. done around 300 miles now after and no problems and runs great.