RAVE valve again

JJinSC

Well-Known Member
Hello SeaDoo Forum!! I have been away a while, but finally got back. I did a search and I know this subject has been discussed some way in the past, but nothing real new.

I pulled my XP (running fine when I shut it off on the trailer) from the water in October and it has been sitting under my house on the trailer since. I went to crank it up to fog the engine for the winter and just got a clunk. The battery was new and had been on the maintainer so was fully charged. I pulled the plugs and tried to spin it and got a clunk. I tried turning the shaft with my hand and it would turn only a certain amount in either direction before it clunked against something a stopped. The only thing I could think of was RAVE valve. So I pulled of the plastic tops to the RAVEs and pulled on the plastic valve cap of the MAG RAVE. It felt fine. I did the same on the PTO side RAVE and it came up much higher. I said, uh oh. I removed the allen screws and pulled the valve and sure enough, half of it was missing. I pulled the head cover and found the broken piece half sticking out of the RAVE port and half sitting against the top of the piston. I inspected and aside from a couple very small dings on top of the piston where it hit, there is no visual damage. I moved the piston up and down by hand and inspected both rings through the RAVE slot. The rings were not touched and neither was the side of the piston. A big sigh of relief. The threads in the plastic cap was stripped which allowed the valve to drop below clearance. I am soooooo glad this happened after it was shut down while resting on the trailer and temps started plummeting and not while the engine was running. Anyways being away for a while and clear of issues on the ski, I have a few questions. I will be checking the shop manual for some of these, but also wanted to get consensus.

1) what would cause the threads to strip? I suspect because I have not cleaned these in a couple seasons which caused them to get sticky. When I pulled the other out to inspect, it was a bit sticky to come out.

2) Where are you all finding OEM parts now? Parts are getting hard to find. RAVE rebuild kits do not seem to have all the needed components. I checked the Sea_Doo Parts store but they have a lot of items NOT available for my model.

3) is SBT a good source and brand for these?

4) I checked the housing, how much play is tolerable or should I just plain on replacing them too?

5) I read where there is supposed to be something to secure the bottom of the bellow, but my ski has never had anything there and when I rebuilt them last, I never put anything there, no wire, spring nor tie. Is this needed?

6) I did not pay close enough attention when I pulled the valves. Can someone refresh my memory on which way the slots are oriented when re-assembling?

7) Since I pulled the head cover do I need to consider new O-rings for the head cover?

8) is any sealant needed on the o-ring around the cylinders?
 
No, the cap thereds did not allow the valve to go in too far. The valve can't touch the piston unless it breaks or someone machined the cylinders too much and didn't trim the valves.
1. The threads strip because hot exhaust gasses get the valve too hot and melt the plastic threads. Either engine running too lean, missing o-ring on the valve stem or too much housing clearance.
2. OSD seadoo or WSM.
3. No, I don't trust SBT for anything.
4. I think @etemplet might have checked this?
5. No, the older 787 have nothing on the bottom. Some add an external o-ring to put pressure on it.
6. Hold the valve at the same angle as the cylinder and you will see how the go. Also they say "TOP" in the casting.
7. Yes, always replace o-rings.
8. Yes, Loctite/permatex 518 on the combustion chamber o-rings. Products and torque are in the service manual.
 
Thanks so much for responding, MikiD!! I see now that that the blades cannot fall in due to stripped threads. I thought that did not seem right, I see that round part at the bottom of the stem prevents that now. So, that means the blade actually broke and fell loose right after I cut it off last. That was a big blessing!!! Glad it did not fall down there while the engine was running. What would cause a blade to break like this? You may have answered that already with your opinion of SBT. These were SBT blades. I do not recall using SBT when I rebuilt them about 10 years ago.
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Well, I received all my parts and today I was going to work a little on putting the raves back together. I picked up the broken piece that I retrieved from the cylinder and noticed that there are two slivers missing from the other end of the broken piece. Picture included. I can turn the engine freely with my hand and hear nothing loose.
I also hooked up the battery and spun the engine with the head cover off. I heard no unusual noises. The $3000 question is where could these pieces be? Any ideas or advice?

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If I was a betting man I would say they went out the exhaust.
The engine hasn’t run since I found the broken piece stopping the engine from cranking. In order for those missing pieces to have gone out the exhaust, are you thinking they were broken off when the engine was running before I shut it off last?

If you were not a betting man, what would you say? 😉
 
I guess the question is when did they break?
They didn't break just sitting on the trailer.

A guess it that they did break when running and the exhaust gasses kept them up or the pistons would be trashed. Once the engine stopped they fell down as there was no exhaust gas to hold them up and locked the engine. Maybe...LOL.
 
Yeah, was thinking the same thing. If you look closely in that last picture, there is actually smooth wear on the broken part between where the two pieces broke off of it like the rings may have been grazing.

I guess I’ll put it back together and pray they went out the exhaust. One more question, is the 518 just used to hold the o-rings in place for re-assembly or does it add to the o-rings sealant purpose? Just trying to figure how and how much to apply.
 
Does anyone have recommendations for cleaning the RAVE slots?
If they have a lot of carbon maybe take the cylinder cover off, rotate the pistons till at bottom, stuff rags on top of piston and clean the rave slots with brake and parts cleaner and a brass bottle brush, clean up with a vacuum? Repeat for other side.
 
If they have a lot of carbon maybe take the cylinder cover off, rotate the pistons till at bottom, stuff rags on top of piston and clean the rave slots with brake and parts cleaner and a brass bottle brush, clean up with a vacuum? Repeat for other side.
Thanks Burt. This is kind of what I was thinking but did not know if break cleaner was good to let get in cylinders.
 
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