Rave Valves Goin Deep

[etemplet]

OK, I'm gonna get deep into these rave valves as one of mine melted. So check this out. Brand new housing worn .011" in only MAYBE 5 hours run time. This is on the failed MAG cylinder valve. I measured all the parts to these valves a while back. There were no issues with melted caps earlier but the ski is pretty new to me and only got in the water in May. I did however, have everything apart twice since June. I recently slotted the valves on this ski so I have some concern there. This is a 96 model. There were no issues with the non-slotted valves. This thing went pretty quick when I put it on the water. Less than 5 minutes running. It was the first time I accelerated to top end and it didn't get there. Started missing at 6500 and dropped RPM to 5500rpm. Held at 5500 and it ran smoothly. A few minutes of nursing the throttle and it was back up to 6500. I rode it for an hour but didn't like the performance... not bad but not what I wanted. 48mph top speed.

Got home expecting to do some checks. Found the rave valve red adjuster laying on top of the engine. LOL Bingo... this might be a clue. I can't rule out that I did not assemble the valve correctly Maybe the spring wasn't in there like it should have been but I am very anal about all such things. As I said, recently slotted the valves which may be the whole problem. OK NOW... perhaps the valve stem rattling around beat up the bore on the new valve body. I checked the PTO Rave valve and the bore on the valve body was about .003" larger than it was when I installed it in July. That is too much wear for me short term with no damage to the parts.

1. could the metal in these after market valves be that crappy causing acelerated wear?
2. could the valve slot in the cylinders be so large and worn that they are allowing the valves to move around too much and beating up the bore?
3. could aftermarket bellows be preventing the valves from opening all the way? (this is more a performance issue but if the valve doesn't open all the way, the o-ring doesn't seal off the hot gas)
4. These valves I noticed had a smaller o-ring than valves I looked at in my spare parts. But these o-rings have plenty of sealing surface. I don't think this is a root cause.
5. I put in some new Iridium plugs and everything is very clean. Plugs look like new not brown. Could I be a tad lean developing heat?
6. The spring was melted into the valve cap in the proper location so I'm pretty sure it was in the slots when I assembled the valve.

For the measurement side of things. My old valve bodies had .010" clearance between the valve and stem and didn't melt anything. Again I am concerned about the PTO cylinder have .003" wear in the short term. Something is going on. I measured a few rave vales bodies I have pulled from other skis. The bore size is as NEW. So I'm thinking it is not natural for these bores to wear so quickly. I am focused on aftermarket quality of materials but I believe these valves are "chattering".

I also noticed that my gaskets have some overlap near the valve and perhaps the valve got hung up which... I'm not sure can happen with the bore holding it in place but I won't rule that out till I do some checks. I will make sure when I go back the gasket surface will be flush with the edges.

I am measuring the size of the slot in the cylinders to rule out problems there. Near as I can tell the valve in the slot has about .035 to .050" clearance. the slot is tapered either by wear or design. I will get more accurate readings later today.

My plan is to install non-slotted valves, I found some red bellows that are .010" thinner and more pliable than what I am currently using. So I am going to install good valve bodies with the more pliable bellows material. I have also ordered OEM Bellows which I had to get from two different vendors.

 

[etemplet]

When I bought the rave valve parts I was new to these skis so don't condemn me please. I noticed one of our vendors talks about Italian bellows? are those acceptable replacements??

 

[etemplet]

I am still trying to get this ski to run as fast as my wife's and I am not giving up. I'm talking the ski out to do some carb adjusting but it runs great might need a little more fuel up top... not sure. As mentioned plugs look like new and I have a little concern about lean. Do Iridium plugs run Hotter? is another question

 

[GGuillot]

I'd put the non slotted ones back in, a new cap to replace the melted one, then go ride. Or did I hear you slotted or machined the old non slotted valves? I hear you on the new housings, but did you replace valves at the same time? You mention about aftermarket valves with inferior metal. Are they aftermarket and you slotted them? I haven't seen the need for slotted RAVE valves yet on my 97', but I think either you cut them too deep allowing more exhaust through or the RAVE valve stems are worn.

On the plugs, I'd stick with the stock NGK's, but I wouldn't think the iridiums would matter either way, it's more a longevity benefit, least in the automotive arena it is.

 

[mikidymac]

To answer your question, I don't know. I can tell you on just the 5 787's that I worked on this year not a single one had slotted raves and I cleaned and put the old ones back in with the original housings. Tow of the 3 got the WSM gaskets and o-rings as part of the complete engine kits and three got OEM o-rings and gaskets.

All 5 have been running all summer with no issues. Honestly I have never had a RAVE problem on any of my skis or ones I have worked on but I can tell you one consistent variable, always OEM valves, housings and diaphragms. I have only used OEM and WSM o-rings and gaskets and never had a ski with the slotted raves that I can remember.

When yours started missing at 6500 then dropped to 5500 and stuck that in my opinion is not a RAVE issue since they open and are done at 4500.

Also to have that much wear in only a couple rides I would suspect soft housings.

 

[etemplet]

To answer your question, I don't know. I can tell you on just the 5 787's that I worked on this year not a single one had slotted raves and I cleaned and put the old ones back in with the original housings. Tow of the 3 got the WSM gaskets and o-rings as part of the complete engine kits and three got OEM o-rings and gaskets.

All 5 have been running all summer with no issues. Honestly I have never had a RAVE problem on any of my skis or ones I have worked on but I can tell you one consistent variable, always OEM valves, housings and diaphragms. I have only used OEM and WSM o-rings and gaskets and never had a ski with the slotted raves that I can remember.

When yours started missing at 6500 then dropped to 5500 and stuck that in my opinion is not a RAVE issue since they open and are done at 4500.

Also to have that much wear in only a couple rides I would suspect soft housings.

I agree with it not being a rave issue and I thought it was carb all the way... especially when it cleared up.

What makes me think it was the rave is the valve was completely separated from the piston with no control at all. How it opened I don't know... if it did open at all. How did it accelerate to 6500 RPM with the valve with no control? I would think it HAD to lift in a lethargic way to achieve that RPM although that is speculation on my part. The ski ran fine just blah on top. I had fun cutting up with it, it wasn't bad in the corners or anything. Strange indeed. I'm going back with the OEM stuff and non slotted valves. I'll see if my wife's ski is suffer the same malaise... I did both exactly the same. I will report back after I take it to the water.

I am also going to have some measurements on the cylinder slots. I will compare all three skis. If I had a new cylinder size that would be great. I love this stuff !!! If I have to... I'll put a bushing in these bad boys but I shouldn't have to do that.

 

[etemplet]

I think either you cut them too deep allowing more exhaust through or the RAVE valve stems are worn.

I'm am a machinist.... everything gets measured including the depth and width of the slot (I had a slotted rave as an example).. This is also how I know how much the bore opened up.

 

[GGuillot]

I'm am a machinist.... everything gets measured including the depth and width of the slot (I had a slotted rave as an example).. This is also how I know how much the bore opened up.

I wasn't trying to knock your machining abilities, but you had something cause a RAVE cap to melt, which we know means enough hot exhaust gases passing through to cause it. You have new housings, the only other variable I can think of is the modification you did to the valve or it's worn.

But maybe I'm missing something, there was someone else on here chasing this rabbit hole of melting several RAVE caps over and over. When he replaced both housings and valves together, not separately, the problem went away.

 

[etemplet]

Sounds like he was shooting in the dark and got lucky. Making modifications on one valve will not affect the performance of the other. Likely the housing bores were larger than .410" That's close enough to .020" clearance and way too much. No doubt there are skis out there with this kind of wear and owners are not encountering any problems at all.

I'm still considering a lean condition on the Mag carb.

 

[GGuillot]

Sounds like he was shooting in the dark and got lucky. Making modifications on one valve will not affect the performance of the other. Likely the housing bores were larger than .410" That's close enough to .020" clearance and way too much. No doubt there are skis out there with this kind of wear and owners are not encountering any problems at all.

I'm still considering a lean condition on the Mag carb.

Back those high speeds out a turn or so and move back in, I'm currently at 1/2 mag and 3/4 pto, lows 1 turn and I'm getting really good performance. I think our carbs are the same, 35-36 pop off blk 80 gram spring, etc.

 

[etemplet]

So with regard to aftermarket, who has good rave parts especially bellows.?

 

[mikidymac]

I would only use OEM parts especially the bellows.

 

[etemplet]

Perhaps I got some bad info... are these bellows getting scarce?

 

[etemplet]

It pays to have 6 rave valves and bodies to choose from. The only 2 shaft bores that were oversize were on the two valve bodies I purchased last month. Close inspection and lots of checking, I didn't see anything out of the ordinary. I noted the gasket could be placed in a way that would interfere with the movement of the valve. To check this I purposefully moved the gasket around on assembly and sure enough... I could lock the rave valve up.
So... valve body bore is (.399") Valve shaft is (.393) I found (.035") to (.050") clearance on the valve blade and the opening in the cylinder. I did find my o-rings were smaller but they sealed just as well. I went back with the larger o-rings though. I ordered OEM Parts that will be in next week. I want to have stash of parts. That's how I roll. We'll see how it goes. It's either those funk ball valve bodies I purchased or I missed something.

One of the manuals I used said to tighten the red cap all the way for the adjustment. I didn't listen but I'm about 1/8" below the top. May head to the water tomorrow. Gonna bring my laser temperature sensor so I can see what's going on with the engine, pipe and all that stuff. It is a good way to check things out.

 

[Sportster-2001-951C-Stock]

AFAIK, it's not so uncommon to hear of melted RAVES on the 787, sure would be nice to get to the bottom of the root cause(s).

I've heard some adjust so a nickle coin sitting on the adjuster is flush with the top. Whatever the adjustment, the RAVE must open completely to seal the blade shaft o-ring against the housing thus to me less spring pressure correlates to a better seal for the o-ring,

If there's insufficient spring pressure and the RAVE opens too quickly as a result, you may experience some temporary loss of power or dead zone?

Also FWIW, one can drill a hole center in the adjuster and insert a rod "toothpick" to detect movement.

 

[Sportster-2001-951C-Stock]

It's been noted some of the Rotax carbs should have a bit more high speed mixture on the MAG carb due to heat from the magneto, I have no proof unless the Seadoo manual advises this. Maybe the best place to observe the cylinder sleeve temp is down low near the base gasket?

Just tossing out ideas, no idea if they make sense.

 

[etemplet]

It's been noted some of the Rotax carbs should have a bit more high speed mixture on the MAG carb due to heat from the magneto, I have no proof unless the Seadoo manual advises this. Maybe the best place to observe the cylinder sleeve temp is down low near the base gasket?

Just tossing out ideas, no idea if they make sense.

Heck no man... all good stuff. Brain Storming is good. You hit on lots of important points. I'm still mulling over the small performance drop with a failed rave valve. Perhaps the cylinder pressure caused the valve to open a bit. There is no way the bellows could work at all.

I found a red bellows on one of the parts skis that is much more flexible than the ones I had on there so I used those.

I'm considering a little tuning on the carbs for this ski (the 96 GTX). Plugs look great though. I might just let my wife beat me for now and do a top end this winter. Compression isn't bad but looking in the rave port and playing around a bit with the rings.... they are worn a good bit. the 96 just doesn't have the PUNCH her 97 has but I just built that engine.

 

[mikidymac]

Some of the aftermarket bellows are too stiff to work correctly just like the carb diaphragms. You want the newer OEM green ones and are still available for $20.24 each. The orange ones are the first generation OEM.

The cylinder that runs hotter is the rear cylinder not the front and is typically set up a little richer on the high speed screw. This is due to the crankshaft actually twisting under load so the timing is actually advanced a little. It took yamaha a little while to figure this out and actually retard the timing on the rear cylinder.

 

[etemplet]

Great !! Well I paid too much for the OEMs but they are on the way. Where are you buying the OEMs??

I'm taking the ski out today along with my wife so she can beat mah azz a-gin. I'm gonna take the 96 (slow poke) this ski out for some carb tuning next week.

 

[mikidymac]

I get all my OEM parts form Peo Caliber seadoo but on my next order I am going with PWC Muscle since hfGreg here said he can match or beat their prices and support the forum.