"Fun" new project-1998 sea doo engine trouble

[sms986]

So long story short I got roped into repairing two jet skis for a family member. One is up and running, the other, a sea doo, is doomed. I have enough know how about engines to do the repair, but I've never done anything with jet skis so I'm limited on the specifics. The engine mn is 5836. My uncle said the engine was replaced by previous owner and smoked very bad. Doesn't look like the engine was replaced. If so, it was an eBay used engine. I found tons of oil in it so I figured I'd better pull it apart. Both cylinders' crankcases were full of oil and the magneto housing was too. I'm thinking a) "new" engine had bad bearings that ate up all of the seals, b) the seals were just worn out, or c) the engine wasn't aligned and it tore up the seals. Either way, thanks to this fancy rotary valve engine, the whole crank will be replaced (it actually looks pretty good). So I'm left with a complete rebuild and I'm in the process of gathering new parts. My only question at this point is regarding the stator and stuff. It took a HEAVY bath in oil. I don't know if these are wet or dry systems, but it looks like it's supposed to be dry to me. Will any of these electricals be any good? I doubt I'll ever be able to dry them off.

 

[GA_Boater]

It's a 2 stroke, so it isn't a wet or dry oiling system. An oil injection system is used and that may be what went belly-up.

The rotary valve is completely separate from the crank and serves the same function as reeds in other 2 stroke. If the crank is good, don't replace it if the bearing and seal surfaces are good.

Oil shouldn't hurt the electrical parts. Clean up as best you can. I wouldn't hesitate to use soap (Dawn) and water with a soft brush on sealed electrical parts. If Dawn is good enough for sea birds, it's good enough for a Sea Doo.

Free operator and service manuals can be downloaded here - http://seadoomanuals.net/manuals/1998-seadoo.php

 

[sms986]

As to wet or dry system, I meant the ignition system. I know that on some dirt bikes/quads I've worked on the rotating components of the ignition system were inside the case with oil-wet systems.

also, in-between the two actual crank cases, there's a third case that houses the gearing for said rotary valve. It looks like this case is always in a bath of oil, so if all of the oil has found its way into the crank cases, it had to be through the seals (which are in the middle of the crank) hence why the crank looks like it needs replaced because I see no way of pulling it apart to replace the seals (welded crank).

I'll try to get the electricals cleaned up and keep my fingers crossed. Thanks!

 

[GA_Boater]

Were both sides, crankcases as you call them, filled with oil or just one side?

 

[sms986]

The seals on either side of that gear are the suspected culprits

 

[sms986]

All of it was filled. Both sides and the magneto case

 

[GA_Boater]

Good chance it's the rotary valve shaft that failed, not the the crank inner seals.

And the seal for the magneto case.

https://www.seadooforum.com/threads/crank-seal-replacement.36180/

 

[sms986]

Regardless, I'll be replacing all seals anyway. I don't like to reuse gaskets and seals that "look" good. Thanks for the replies... Gives me some brain food.

As for the rotary valve...

Is there any advantage to this at all?

I honestly thought it was incredibly stupid when I first tore this motor apart. Same function as reed valves, but not only have you introduced a couple dozen more parts, but you have compromised the reliability of the engine with things like the rotary valve seal, additional bearings, and a rotary plate that is prone to getting scratched up and leaking by.

Seems to me like a "hey look, we re-invented the wheel" type deal.

What is the advantage of the rotary valve?