jpotts

Hello,

I am currently working on a 670 motor right now, and I have some questions. (I have a link for pics below) I have worked on a few Sea Doo motors (witch are identical except for the the cooling)

First...
I bought a sled (96 Summit 670 w/ 57xx ish... miles) with a blown motor. The two PTO bearings were roached on it. All of the balls and plastic cages were gone. No sign of them (not even in hammering out the cases, pistons, cylinders, other bearings) I think the webs kept that stuff from going in.

Open inspection, here are some of my observations...

1. The crankshaft pto web had drifted toward the oil seal, so the pin was only halfway in the PTO web. It stopped pulling out once the web ran into the side of the case (note pictures) It either got hot or worked its way out. (GETTING A NEW CRANK AND REPLACING IT)
2. Upon reassembling the pieces I noticed that only the PTO side bearing had moved outward (possibly forcing the oil seal out and making for a bad scene) The PTO bearing closest to the web stayed in place.
3. Everything on the top seemed okay EXCEPT for the fact that the pistons didn't match MAG side was 77.94 (STD) and the PTO was 78.19 (.25mm Over) Both cylinders, head seemed okay. The PTO side piston took some debris on the walls of the piston, so I'm probably going to replace at least the PTO side.
4. The PO took the bottom plate off the oil pump opening up the seal and the piston at the bottom. Don't know if that going back together... never took one apart... Afraid to put it back together.
5. The groove for the retaining washer in between the bearings has worn into more of a trapezoid than a square notch (see pics)

Please look below for pics.
670 carnage pics....

So here are my questions...

1. What do you think caused this to happen? I think it lost an oil seal, got hot, pulled the bearing, heated the webs and split freezing the motor. OR.... PTO outer bearing got hot (from being bad), moved outward, pushed the seal off, heated the webs and split freezing the motor.
2. Could it be clutch related taking out the bearing to begin with?
3. Can I reuse the cases? Should I clean up the ridge that is on the inside edge of the PTO side (or does that belong? Its right up against where the web ran into the side of the case)
4. What do you feel about having unmatched bores for the pistons?
5. Suggestions on the oil pump (I kind of like the possibility of not blocking it off just because of ease)
6. Is that groove in the case going to be okay? It still provides a positive stop for the bearing.
7. What do you recommend sealing those cases off with? I have heard Three bond 1194, 1190, 1211. I have heard Locktite 518, and I have heard Blue RTV (I would never do that though!)

Thanks for all of your time and patience reading this (and replying hopefully)

Jason P

Mr. Bill

The picture of the crank shows that the counterbalancer flywheel has spread apart and made the overall length of the crankshaft longer on the end showing the damages ( look at the gap between the rod and the thrust washer next to the rod ).
I am not sure why it happened, but a sudden impact or torque could be the reason that it beat the retainer bands to death where they sit in the cases by the two bearings. Once the crank starts moving forward and backward within the cases, it acts like a hammer with every accelleration and deaccelleration of the engine , hammering the crankshaft and eventually the retainer rings and the case grooves. The crank becomes sloppier with each hit as it slowly spreads apart at the crank pins and grows in length.

I would find a set of decent used cases and an oil pump and throw that case onto the scrap aluminum pile. A newly rebuilt crankshaft should solve the crank problem. It could be a bad clutch or driveline causing this problem, or it could be that the last crank rebuilder was not experenced enough to know when a pin presses into the crankshaft too easily or he just did not care enough to fix the problem with the pin fitting too loosely into the counterbalancer flywheel on the crankshaft.

The actual bore difference is only .010, not enough to matter much, if any at all, although I perfer to have the two pistons equal in bore size.

New cases, I use Loc-Tite 518, but used cases I use 3 Bond 1211.

Bill O'Neal
WCM