96 XP Revival

[JeremyD615]

So I spent a few hours out on the water with this ski today, and it was slow enough on the lake to play around with some things to try to get my last few hundred rpm back.

I readjusted my throttle linkage before I took it out today, and there is no slack in the cable and it’s gully opening the throttle blades. I think I can scratch the cable off the list of things that could cause this...

I played with the water regulator. I started at the factory setting of three full turns out. This is where it’s been set the whole time, but I went back and verified that it was correct. Max rpm was 6310. I moved the cap to flush, and got 6320. No real change... I tried to take it three or four clicks past the factory setting, and I got 6340. I also verified that I still have water flow and that it’s restricting it at full throttle. Im pretty sure we can scratch the water regulator off of the list too.

I rebuilt both rave valves not long after I got the ski, but I couldn’t remember whether it was before or after everything went haywire. I pulled the caps, and everything appears to work correctly, but this is the only machine I’ve got with the RAVE system, so I don’t have anything to compare it to... Both valves seem to move smoothly and easily with the cap and spring off, and there is no gunk or obvious leaks in the bellows. I tried the raves turned all the way in, one turn out, and flush with no real change in max rpm. It stayed right in the mid 6300’s. I still wasn’t super confident that the raves were functioning the way they should though, because when I first had the ski on the water, before the fueling issues, it had such a strong upper-midrange and peaky feeling that just isn’t there anymore. This ski feels about the same speed as my 95XP, and that was confirmed with a GPS top speed of 51.6mph. That’s actually just slightly slower than my 720 ski.

To really rule in or out the rave valves, I pulled the caps and went for a run without them. Of course the ski sputtered and ran like crap, and it was maxing out at about 4500rpm. It wouldn’t even get all the way on plane. Then after I got it turned around and headed back to the dock, I decided to try to bounce the ski enough to unload the pump and see what happened... It got over the hump almost instantly, and revved all the way to 6600 before I ran out of room and had to let off. Eureka! It appears to be the rave valves that are causing the missing rpms, but I can’t figure out for the life of me why... I tried screwing the bellow in and out to see if I could get more travel one way or the other, with no perceptible difference, so I screwed them back hand-tight. Does anyone have any insight into what would cause the raves to not open with the caps on, even though they are clean, have new bellows and O-Rings, and move freely when I push and pull on them by hand? This is my last performance gremlin to deal with and the ski will be ready for me to get back into the cosmetics, so hopefully it’s something I’m just missing.

 

[Matt Braley]

Does it still have the stock impeller, intake grate, sponsons and nozzles? Your sure there is no water or smoke leak going on under the seat, right? I know you looked before but check out the coupler between the chamber. You can slide the seat back a little and see if the fresh air changes rpm. Has it been aligned? Side tension on the drive shaft can cost a few rpm. High speed needles on the carbs are closed? Is the nozzle trimmed up or down? If it's stuck down that will cost some rpm too.

 

[JeremyD615]

Does it still have the stock impeller, intake grate, sponsons and nozzles? Your sure there is no water or smoke leak going on under the seat, right? I know you looked before but check out the coupler between the chamber. You can slide the seat back a little and see if the fresh air changes rpm. Has it been aligned? Side tension on the drive shaft can cost a few rpm. High speed needles on the carbs are closed? Is the nozzle trimmed up or down? If it's stuck down that will cost some rpm too.

It appears to be a stock impeller and nozzle with an R&D grate. I checked for exhaust and water leaks today, and it’s dry as a bone. I swapped the WCV housing, and checked the hoses and couplers last night. Everything is snug and leak free. It hasn’t been aligned, but since it ran to full rpm before, and ran up to rpm with the rave caps off, I’m really thinking it’s something with those valves... I have a working VTS in it now, so those rpms are all trimmed most of the way up... For some reason it seems like the exhaust pressure is just not high enough at the piston to overcome the spring tension. I know that’s weird, but without the springs in there it pulled hard like it should...

 

[mikidymac]

How are you checking rpm? To be accurate you need something like a tinytach.

 

[etemplet]

I had similar issues with both our 96/97 GTXs but I was about about 6400 RPM. What I ended up doing was doing the modification to the rave valves. There was a bulletin on this and someone posted it. I replaced the rave valve housing with the different type and installed the slotted rave valves. My wife's jet ski performed my better right away.... as usual. Her's is always faster than mine. I measured the size of the rave valve bodies and the bores were worn so there was almost .020" clearance, new valve bodies only have about .006" if I recall correctly. It was an adventure.

 

[JeremyD615]

How are you checking rpm? To be accurate you need something like a tinytach.

I do have an induction tachometer on it. The rpms were read back using the max rpm function on the gauge, so I think they are pretty accurate.

I had similar issues with both our 96/97 GTXs but I was about about 6400 RPM. What I ended up doing was doing the modification to the rave valves. There was a bulletin on this and someone posted it. I replaced the rave valve housing with the different type and installed the slotted rave valves. My wife's jet ski performed my better right away.... as usual. Her's is always faster than mine. I measured the size of the rave valve bodies and the bores were worn so there was almost .020" clearance, new valve bodies only have about .006" if I recall correctly. It was an adventure.

I knew there were revised valves with the slots, but I didn’t realize that they had a revised housing as well. I’ll have to do some research on that. It’s just so strange that they worked as they were supposed to before I put the new bellows and O-rings on them. I may try to throw the old ones back on and see if it does anything before I start buying new housings and all that, but I appreciate the info. It gives me something else to look at.

 

[etemplet]

You may be onto something as I now remember the bellows were more stiff on one application. That may cause problems. Great idea !!

On a side note I have a GTX RFI I don' t think the rave valves are opening properly. I'm gonna trick that one this weekend. LOL Good Luck !!

 

[mikidymac]

Where did you buy the bellows?

I know some of the cheap aftermarket ones are too stiff and don't work correctly.

 

[JeremyD615]

Where did you buy the bellows?

I know some of the cheap aftermarket ones are too stiff and don't work correctly.

It was an OSD kit with the bellows and O-Rings, and they look like the revised green OEM ones, but they are quite a bit stiffer than the red ones that were in it.

I pulled both raves last night, and I did have a leak on the mag cylinder that I didn’t notice because I hadn’t yet cleaned up the oil from the first time I did the valves. That’ll teach me to not clean up after myself... there were no holes or cracks in the bellows, so I’m hoping that I just didn’t get the bottom sealed well on the first go around. It wasn’t that much oil though, so I have a feeling it’s the clearance between the shaft and the housing... I threw the old red bellows back on them and put it all back together to see how it does, but I may have to just order the whole kit with the newer slotted valves.

 

[etemplet]

I did the same thing to mine. I wasn't sure the red ones were OEM but they were definitely more pliable and flexible. Also.... I found this little tidbit. It is possible to pinch the valve blade when installing the body so it binds and doesn't slide up and down freely. This was a gasket issue. Melted my piston.

I also measured the slots in the cylinders six was from Sunday to determine if they were worn too much. I probably should measure all the ones I get in here to have a working range. Data is a good thing.

 

[JeremyD615]

Yeah, I wish I had some data to work with, but I’m just going to have to try it and see what it does. I don’t think anything was pinched, because they seemed to move pretty easily by hand... we will see when I get it back on the water tomorrow.

 

[etemplet]

I swapped water control valves with another ski. I don't think it will make a difference but I saw something oily under the WCV. Not sure what it was and I have others so... I'm gonna give it a go.

 

[JeremyD615]

I had a spare WCV as well. I swapped it the other day and it didn’t make a difference on mine, but good luck!

 

[etemplet]

Hey.... gotta do sumpthin.... ya never know. Looking at my shaft seal on the slower GTX and it's way off. I've never pulled the pump on this ski but I'm gonna check alignment. I might even put something "go faster" on there. Time to start cheating.

 

[JeremyD615]

So I got it back out today and it ran without any issues, but the tips end still isn’t there. It was a busy day on the lake, so it was way too choppy to get any meaningful runs in. It seemed to feel a bit better than it did, but there was 1-2ft chop almost the whole time we were out there, and I had one of the kids on the ski with me, so I didn’t push things. I’ll try to get out in my sheltered cove tomorrow and see what it does, but I have a feeling I’m going to have to replace the raves with new ones. This ski is getting expensive fast!

 

[etemplet]

How scarred up are the raves? Make sure the valve guide in the rave bodies are not worn out. Are you going with the slotted ones?

 

[JeremyD615]

They have a bit of scarring on the sides of the valve, but they are more what I would call scratches than scars. The flat faces are fine. The aluminum housings look fine, but there is definitely some play when the valve is up. I also noticed that the new o-rings are not terribly snug on the stems. They appear to make contact all the way around, but the O-Rings can slide off of the stem if you hold it upside down.

I know what the rave valves do, but I’m having a hard time figuring out exactly how they function. Exhaust gas seems to flow around the stem and into the bellow/piston, which moves the valve into the up position. Spring pressure controls that movement from the other side of the piston. The part I’m having a hard time with is the O-ring. The gasses would have to flow around the O-ring to get into the bellows, and the only function it seems to have is to act like a bumper when the valve bottoms out in the housing and possibly to wipe some excess oil from the walls of the housing.

If this is correct, I can’t see how any scarring or wear between the stem and the valve guide would stop operation. The pressure to move the valve would be focused on the piston and bellow, and as long as there is nothing binding and the valve moves freely, it should function. On my ski, the pressure does not seem to be rising high enough to overcome the spring in the cap, but I don’t know how that’s possible since there’s really nowhere for the pressure to bleed off since there are no leaks.

I think if I replace the whole rave assemblies, it will probably work just fine, but I’m stumped as to what the problem actually is here.

 

[etemplet]

It's been while since I looked at them. The valve body on the upgrade was different. Also, as I mentioned, the bore size on the rave housing was about .020" on mine. I'm thinking they valve Outside Diameter was .391" and the bore was .411" . Problem I had was I bought aftermarket parts and within a couple of hours the valve body was worn on two of them and one was already .409" So aftermarket on those.... don't do it. I'm thinking about installing a bushing in those. Look into the slotted raves. I'd install those since you are trying to address a performance issue. My wife's ski responded nicely to the changes. Her's is a 97 GTX.

Here is a link to my thread. Rave Valves Goin Deep

Here is a great write up on the forum with pictures How to service Rave Valve---Pictorial---

 

[etemplet]

DUDE !!!!!!!!!!!!!!!!!!!!!! I replaced the water regulator on my GTX on Friday. Man that thing was impressive. Heck of an improvement for certain. Go figure !!! I wanted to get some of Sissy's ski today but she punked out. I'm a whup dat azz next time out and I haven't had to resort to cheatin... yet.

 

[JeremyD615]

I’m glad that did it! Those water regulators can be finicky little bastards... I was hoping that was my issue too, as I had some issues with it, but I’ve swapped the whole exhaust minus the head pipe at this point... I think it’s safe to say the exhaust is all sorted out now...

 

[JeremyD615]

That just got me thinking. The only things left in the ski that haven’t been swapped are about to be the crankcase and the cylinders...

So far I’ve replaced:

Complete front Ebox/MPEM
Battery
DESS Post
VTS/Start Stop Switch Assembly
Throttle Cable
Stock Airbox/Flame Arrestor/Bracket
Voltage Regulator
Fuel Lines
Oil Lines
Complete Carb Swap
Water Seperator/Filter
Water Lines
Rave Rebuild
VTS Motor
Water Control Valve (Housing and all)
Waterbox
Coupler Hose
Rear Exhaust Hose
Fuel Selector
Fuel Tank
Battery Kill Switch
Ground Cables
Vent Check Valve

I’m going to order new rave valves this week, so those will be entirely new, as the bellows, O-Rings, and retaining springs are already new. I’m literally running out of parts to change over... I’m thinking now that I could have just pieced a whole ski together and thrown it into an empty hull...

 

[etemplet]

I sure don't understand the Water Regulator. I took that thing apart and spent a good bit of time working on it and trying to figure out how it does it's job. Perhaps the confusion for me was that is wasn't working properly.

 

[JeremyD615]

I got out on smooth water today, and it’s running much better with the old red bellows on the raves. I’m finally back to the top end rpm I had before... It’s running up to 6630rpm now and GPS’d 54. I’m still going to swap the valves out for new ones, but I found it really interesting that the bellows were what was causing the rpm drop. Has anyone else seen this kind of reaction moving to the new style stiffer bellows?

I’m thinking that there is probably a couple hundred more rpm to be had, and 54 seems a little on the slow side, but it does have that grate on it, so this may be all I can get.

 

[etemplet]

People don't realize all it takes to get these ski where they need to be. But one learns so much in the process. Priceless.

 

[JeremyD615]

Just a minor update with some before and after pics... I’ve still got some vinyl to replace since the lower hull decals I ordered have already come up in a few places, but the cosmetics are just about done! The weather here in Nashville is going to be bad all weekend, so I’ll get the replacement vinyl and another coat of polish on it before it clears up hopefully!

Before:

After: