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  1. #1
    Top Dog pdxrealtor's Avatar
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    question on rave valves and other

    I noticed that the red screws on top of the rave valves are screwd down well below the top of the black plastic cap. I was reading about rave valves and noticed that everyone says normal setting is to have the red screw even with the top of the black casing.

    Would someone have done this to correct a problem? Would they cause an exaust leak? (I have one at the back cylinder)

    What exactly does the adjustment of these do? UP VS DOWN ? Even with the black casing?

    I have a 97 xps.......

  2. #2

    Re: question on rave valves and other

    Seadoo suggest they should be even with the top of the palstic but any dealer that I have talked to say to screw it down all the way, all it does is give you a bit more compression in the cylinder.
    Is there black oil leaking from the back rave??
    If so just pull em apart clean all components and get 2 new gaskets tighten the screws down!!
    Good Luck

  3. #3
    Top Dog pdxrealtor's Avatar
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    Re: question on rave valves and other

    Quote Originally Posted by djmaincheese
    Seadoo suggest they should be even with the top of the palstic but any dealer that I have talked to say to screw it down all the way, all it does is give you a bit more compression in the cylinder.
    Is there black oil leaking from the back rave??
    If so just pull em apart clean all components and get 2 new gaskets tighten the screws down!!
    Good Luck
    Thanks! There is black oil leaking from the rave, but there is also clearly exaust stains in the same area.... I thought it was coming from the gasket between the manifold and the engine... could it just be the rear rave valve?

  4. #4
    Top Dog UaVaj's Avatar
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    Re: question on rave valves and other

    Quote Originally Posted by djmaincheese
    Seadoo suggest they should be even with the top of the palstic but any dealer that I have talked to say to screw it down all the way, all it does is give you a bit more compression in the cylinder.
    Is there black oil leaking from the back rave??
    If so just pull em apart clean all components and get 2 new gaskets tighten the screws down!!
    Good Luck
    What are the advantage and disvantages of each position. Please explain in further details of us noobs.

  5. #5
    PWCToday Regular cdoxp800's Avatar
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    Re: question on rave valves and other

    R.A.V.E. Inner-Workings
    (*Excerpts from the SD Racing Handbook )

    For a 2-stroke-cycle engine to have high power capacity at high crankshaft speeds, a high volumetric or breathing efficiency is required and the fresh charge losses must be minimized. The result is achieved by opening the exhaust port early and utilizing the resonant effects of the tuned exhaust system to control fresh charge losses.

    When an engine of this design is run at a high speed, efficiency falls off quickly. The relatively high exhaust port effectively shortens the useful power stroke and because the exhaust system is tuned for maximum power, there is a large increase of fresh charge losses at lower speeds. As a result, the torque decreases along with a dramatic increase of the specific fuel consumption. Higher torque along with lower fuel consumption can be obtained at lower engine speeds if the time the exhaust port is open is shortened.

    Bombardier-Rotax has patented a remarkably simple system to automatically change the exhaust port height based on pressure in the exhaust system.

    Located above the exhaust port is a guillotine-type slide valve. This rectangular valve is connected by a shaft to a diaphragm which is working against a return spring. Two small passages in the cylinder just outside the exhaust port allow exhaust gas pressure to reach the diaphragm.

    To the outside of the return spring is a red plastic adjustment knob. Turning the adjustment in or out changes the preload on the return spring which, in turn, will change the RPM at which the R.A.V.E. valve opens and closes. As the throttle is opened and the engine begins producing more power, the pressure against the diaphragm will overcome the pressure of the return spring and the R.A.V.E. valve will open.

    The R.A.V.E. valve does not allow an engine to make higher peak horsepower than an engine not so equipped, it can however make moving the peak horsepower higher practical, because of its effect on the rest of the power curve.

    (*End excerpt.)

    R.A.V.E. Valve Adjustment
    The actual R.A.V.E. valves are contained within the 2 black caps you have atop your 2 cylinders. There is a water regulator with a R.A.V.E. type adjustment cap on it. Most have found that screwing this all the way in, creates the best performance. This doesn't regulate the water actually, but just how much pressure can be put on the regulator inside the cap before it does regulate the water. Here's a quick guide to adjusting them for optimum performance:



    For acceleration: Cylinder R.A.V.E valves DOWN

    For top speed: Cylinder R.A.V.E. valves UP

    Stock 95/96 Engines: Cylinder R.A.V.E. valves UP

    Stock 97 Engines: Cylinder R.A.V.E. valves DOWN



    Changing the RAVE valve position is only needed if your boat is a Limited class race boat, or a Superstock/Modified class race boat. The change is not really noticible as it changes your exhaust port timing by +-(50-100) RPMs.

    You will not gain more MPH, RPMs, or horsepower by changing the position of your valves, but you will change the powerband from "Point A" to "Point B". On 1995/1996 800 Engines, put your red cap flush with the top of the cap. On 1997 800 Engines, put the red cap all the way in (Don't force it all the way down, it does have a stop a little past halfway which is down). Due to the different impellers and ignition curves from the 95/96 and the 97 800 engines. Sea-Doo recommends this for maximum performance out of your engine. The 1997 800 Engine is actually more towards top end. This is apparent in the SPX which is .4 MPH faster than the 96 XP. Thus to compensate for the small loss in bottom end, they changed the powerband a little bit to get that back.

    Cylinder Boring
    In its stock configuration the R.A.V.E. guillotine has a minumum of 0.5 mm (.020 in) clearance to the cylinder bore measured at the center line of the cylinder. This is the minimum production clearance.

    There is only a first oversize piston available for the 787 engine. It is 0.25 mm (.10 in) larger in diameter than the stock piston. When the oversize is installed, the guillotine will have a minumum clearance of 0.375 mm (.015 in) with the cylinder bore. This is a minimum operating clearance the guillotine should be used with. Clearance less than 0.375 mm (.015) will require reworking of the guillotine to achieve a proper clearance and radius (in other words.. have a dremel tool handy).

    Note: When boring the cylinder on the XP 800 watercraft with the 787 model engine, the engine displacement will be 785.56 cc's after boring and honing. The engine will no longer be race legal for 785 cc class racing. In order to maintain legality, have your local SD dealer re-sleeve the cylinders and install stock diameter pistons.

    R.A.V.E. Valve Cleaning
    The R.A.V.E. components should be periodically checked. The R.A.V.E. valve requires cleaning of the carbon deposits. Cleaning intervals depend on the riding style of the rider, and the type of oil used. Usually its around 30-40 hours you should clean your R.A.V.E. valves, though. If you're using a/the non-synthetic SD oil (which SD has recently said is OK to use), then you might have to clean your valves more often, as non-synthetic oil doesnt burn as well as synthetic.



    Tools Needed: 10mm Box Wrench, 5mm Allen Socket or 5mm Allen Wrench, Carb Cleaner or Solvent, Soap and Water, Blue Loctite, Safety Wire or Zip-Ties (Small)

    First pop off the caps by removing the clips on top. Hold on to the cap, because those springs will shoot to the moon. Take off the cap, while making sure you don't lose the spring. Taking the rear one (PTO) off is a lot simpler than, taking off the front (MAG) one. For the rear one, just take a 5mm allen wrench and take out the bolts. The valve should pull right out. If you are going to reuse the gasket (Which I highly don't recommend unless it is REALLY needed), then make sure you don't rip it as you pull the valve out. Don't worry, you aren't going to break the cylinders or anything. The gasket is just glued on real good. Now pull!

    The MAG valve, must be disassembled to be taken out. Get a 10mm box wrench, and unscrew the cap off of the valve. Don't worry about the valve falling into the cylinder. It has a backing on it to prevent this from happening. Once you have this done, then take the allen bolts out. Take the spring off of the diaphragm and set it aside. Once again, if you want to save the gasket (Which once again I highly don't recommend), then don't tear it as you take it out. Look inside the housing where the diaphragm meets the housing. There should be a white zip-tie there. If there isn't you must put a new zip-tie or safety wire there. This is extremely important on High-RPM engines, as the diaphragm will blow off under high-pressure if nothing is there to support it staying on. I've seen many stock ski's without this from the factory, and they come back with leaks with only 5-10 hours of use on them. So check yours. This is apparent on most new 97 models.

    Alright, you've done it! You've gotten the valves out. Now the cleaning part. Your valves should be pretty black, and if you're lucky, you can still read the word "Top" on both valves. If you are going to replace the gaskets, then unscrew the PTO valve out of its housing. First though, move the valve side-to-side while it's in the housing. If it moves more than 1/4" either way, you must replace both the valve and the housing. If you continue to use the valve, you could wear away the cylinder clearance for the valve. If you are really mechanically inclined. Take the removed valve and stick it into the port. Take a 0.17 feeler gauge and put it in-between the valve and the cylinder. If there is more clearance than 0.15", then the cylinder has too much clearance for the valve to function at it's peak level. If this is so, then the cylinders must be completely replaced if you wish to get the maximum amount of power you can out of the valve. Check for clean passages between the exhaust port and diaphragm chamber. If cleaning is necessary, use solvent to remove the deposits. Also check the diaphragm for punctures, and replace it immediately if it's damaged. You can use a good contact cleaner to clean off the valve, but solvent works the best. Clean the orange diaphragm with a non-rubber melting contact cleaner like carb cleaner. Or you can just wash it in soap and water. Whatever you see as easier.

    If you are this far, then you've made it past the cleaning part. Now for the installation. On the MAG side, make sure your valve O-Rings look good before reinstallation. On the front cylinder, put the valve into the port. Set the gasket on top. If you have the new gaskets, then you don't have to worry about lining up the holes. But if you are reusing old ones, then make sure that the small hole in the gasket lines up with the hole on the RAVE housing. Next put the O-Ring on the valve. Now set the housing on top, making sure that the small relief hole lines up with the one on the cylinder (If this sounds confusing, than consult your Shop Manual. If you had one, you wouldn't be reading this either.). Now screw the cap onto the valve with your finger, until finger tight. Now get a 10mm box wrench and tighten the cap, until it is good and tight. If the cap breaks, than the cap was no good to begin with. You'll have to get a new one. Then put some blue loctite on the allen bolts and put them in.

    On the PTO side, you can assemble the valve before you put it in, which is a whole lot easier. Just use the same method as above. Put blue loctite on the allen bolts and your set.

    Hope this helps you out!!!

  6. #6
    Top Dog pdxrealtor's Avatar
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    Re: question on rave valves and other

    Thanks! It does help....

  7. #7
    Top Dog UaVaj's Avatar
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    Re: question on rave valves and other

    awesome info. should a link in a seadoo tech sticky

  8. #8
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    Re: question on rave valves and other

    Awesome tutorial!!!!!

  9. #9
    Top Dog UaVaj's Avatar
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    Re: question on rave valves and other

    Quote Originally Posted by cdoxp800
    R.A.V.E. Inner-Workings
    (*Excerpts from the SD Racing Handbook )

    R.A.V.E. Valve Cleaning

    The R.A.V.E. components should be periodically checked. The R.A.V.E. valve requires cleaning of the carbon deposits. Cleaning intervals depend on the riding style of the rider, and the type of oil used. Usually its around 30-40 hours you should clean your R.A.V.E. valves, though. If you're using a/the non-synthetic SD oil (which SD has recently said is OK to use), then you might have to clean your valves more often, as non-synthetic oil doesnt burn as well as synthetic.
    Does this means I can safely use 2-stroke mineral oil for my stock 96 787. I just have to clean the rave vales more often - say every 20 hrs or so???

  10. #10

    Re: question on rave valves and other

    I just wanted to say thanks for the post. I was having some trouble with my 97 xp and followed your tutorial and was able to get it back working great. I am by no means a mechanical person so it says a whole lot about your instructions that I was able to fix it. Thanks again.

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