Crankcase Repair

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Another marine repair. My buddy is absolutely obsessed with anything that goes on the water, so he brings this over, "can you fix it? Id really like to not have to buy another" Its the lower half to some 900 triple jetski. From all appearances, the oiling in this poor two stroke went out, and nuked the piston. Skirt came loose, and helped itself out the bottom of the crank, with a gentle nudge from the big end of the rod. I would have hated to be out on the water when this happened. Out of 10, id rate my repair at like a 6 or 7, i just knocked the outside down so he could finish sanding/polising it up.YEAH RIGHT lol. Enough talk, heres a few pics.
Reply:Good job on that repair. I've done the same to motorcycles and it doesn't always need to be pretty. I'm certain that lower case would set him back a few bucks if needing replacement....Kinda surprised to see friction bearing saddles in the case of a small two stroke engine myself, but never have been around watercraft.SlobPurveyor of intimate unparalleled knowledge of nothing about everything.Oh yeah, also an unabashed internet "Troll" too.....
Reply:They arent. They are machined saddles for full ball bearings, pressed onto the cranks. Much like a dirtbike, but permanent to the crank.
Reply:Thanks, the carbon trails in the saddles looked like friction bearing imprints. I've not seen anything but ball bearings on small two strokers myself.SlobPurveyor of intimate unparalleled knowledge of nothing about everything.Oh yeah, also an unabashed internet "Troll" too.....
Reply:No, the bearing section is gigantic though lol. The approx width per inner saddle is 3 inches, two of which are part of the large roller bearing system. Complete with locking rings in the bearing channels to help eliminate crank walk.
Reply:Theres usually a labyrinth seal between the two bearings between each cylinder to keep the cases from pumping air/fuel charge from cylinder to cylinder. They are pretty wide, between each cylinder you have 2 ball bearings and the seal. If the seal fails you'll get an engine that won't tune or idle properly because each cylinder is trying to steal the air charge from the cylinder next to it when the crankcase pressurizes.
Reply:Usually, you have to buy BOTH pieces. They are finished in pairs (upper and lower).
Reply:Yep, you were right. The slots in the bearing bores are for the seals, and not a locking ring. My mistake, there was a "race built" ski he put together that had lock rings in it. Took it over and threw the crank on it, no interference, and mic's out to almost the sameclearance the other unmolested bores gaiged out. So I think I did alright on this one. "Hydrotested" it with water and no leaks or weeping. We will know for sure once it becomes pressurized.