https://pinside.com/pinball/forum/topic/banzai-run-club-banzaiiiiiiiiiiii/page/3#post-4195199

It looks like you start by drilling four rivets, then pry the top off.

Look at the disassembled top, there are the four mounting screw holes and smaller holes beside them.

On your unit, where those small holes are located you see the tops of rivets.

Drill the top of the rivet off, and use an appropriately sized punch to punch the rest of the rivet out.

Pry the gearbox apart, so that you can access the gears, then I would use a toothbrush and some degreaser to remove the grease that is now as hard as tar.

When all the tar-like grease is cleaned off the gears, apply fresh grease (I use super-lube multipurpose synthetic grease). Apply the new grease sparingly, just enough, not too much.

Then the motor bearings might need a drop of oil. You already have the motor off of the gearbox.

On the motor see if you can get a single drip of oil on the shaft and the top and bottom brass bushing. You want the shaft of the motor going up to that tiniest 6-tooth gear to turn as freely as possible.

Oil! The correct oil for this is 3-in-one MOTOR oil... this is different than 3-in-one oil, buy it at home depot or lowes.

Then you'll need to squeeze the gearbox together and either get rivets to hold it together, or maybe some really small screws, like 4-40 with nuts and washers. Use loctite (blue) to make sure the new nuts don't unscrew themselves later.

This isn't particularly easy, but it appears that this motor is unobtainium right now, so it might be worth the hassle.

Good luck!