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  1. #1
    PWCToday Newbie
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    Sep 2009
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    Washington D.C.
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    Rave Valve Bellows keep melting

    I have a 97 GTX (787cc) and one of my RAVE valve bellows (rear cylinder) keeps melting after about 10 hrs or less. When I pop the cover the red piece (adjuster),valve piston are melted. This has happened 3 times. One time the cover was melted. The engine still runs but not like it should. What would cause this to melt? The front RAVE valve has never melted. The sliding guillotine valve (paddle) looks OK but the o ring was melted.
    Thanks!!

  2. #2
    PWCToday.com Is My Home Away From Home Grumpy Old Guy's Avatar
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    Dec 2003
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    Re: Rave Valve Bellows keep melting

    This happens when the clearance between the rave housing & the rave valve stem get too much clearance & the exhaust heat get's thru & melts these parts.

    Replace both pieces.
    Mikuni Carb Service/////////Offering Repairs on all Mikuni Carbs///Cleaning/Rebuilds/Freeing up Sticking Throttle Shafts & Accel Pump Repairs

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  3. #3

    Re: Rave Valve Bellows keep melting

    what dan said, in extreme cases, ive seen a few, that the PV sliding surface inside the cylinder has worn, and too much clearance there has let heat by to melt the bellows also
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  4. #4
    PWCToday.com Is My Home Away From Home Mr. Bill's Avatar
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    Re: Rave Valve Bellows keep melting

    I agree with the above statements and will add to that by relaying a story I have about a melting rave valve. The first thing I did was to replace the complete rave valve assembly parts and then I swappped the two rave valves by moving the mag rave to the pto clyinder, and put the rebuilt mag rave valve assembly to the rear clyinder. Guess what ? After a bit, it melted the rear pto clyinder rave valve piston again. So, I decided to rebuild the carbureators to see if the pto clyinder carb had an obstruction of some sort in any of the fuel inlets or possibly something blocking a jet or whatever, causing the pto clyinder to run hotter than normal. After a few hours, it melted the rave valve piston again. By then, I was becoming frustrated as was my customer. I then swapped out a 787 complete clyinder in place of the clyinder that was on the motor, repaired the pto rave assembly again and after that, no more melted rave valves.
    I surmized that poor maintence of the rave valves had allowed the carbon deposits on the rave valve surface to act as though they were sandpaper as the valve moved up and down in the clyinder rave slot giving it too much clearance between the slot surfaces and the valve surface and that allowed heat to transfer up and into the rave valve assembly above. Carbon is a very abrasive substance and aluminum is not a hard metal but rather a soft metal.
    I remembered that when that paticular boat came into the shop the raves were extremely dirty with alot of carbon buildup on them besides having a melted rave piston. ( the piston is the part that you attach the top of the diaphram to in case you were wondering ).
    We often take in Sea Doo's were the maintence of the raves has never been done since new and often we find them stuck in the slots and unmovable. I have had extreme cases where after trying everything possible to pull it from the slot, like soaking in carbon remover while still stuck in the slot did not loosen it enough to pull it out. All the tapping side to side and soaking would'nt budge it. I have even placed a special fine threaded sleeve that I made onto the threads of the top of the rave valve stem, then used pry bar leverage to no avail. At that point I got out the slam hammer ( dent puller ) and tried that clamped down over the special sleeve to yank it out, which has worked for me before in this situation, but sometimes just snaps the threaded end of the rave stem off at the base of the threaded area leaving the valve paddle and broken stem still stuck in the slot. My next move was to drill a 6mm hole down into the middle of the stem, thread the hole a whole inch or so deep and run a 6mm bolt into the hole to use as a place to grab the bolt head with the slam hammer and eventually get the valve to come up and out of the slot. This was a very time consuming rave valve rebuild job and I had to charge the customer twice the normal fee for a routine service job that also includes rave cleaning amoungst many other tasks of a "normal maintence service job".

    Sometimes these simple failures of regular maintence can become expensive. The lesson here is keep a regular maintence and service schedule and such problems will never happen to your rave valve motor or other parts such as the jetpump oil change and pressure test to keep an eye on any possible seal leakage that would allow water into the jetpump. Lubing the driveshaft bearing and pto, carb rebuilding, good fuel lines, unclogged fuel selector valves and keeping water out of the gas tank is all very important to assure a long lasting Sea Doo that will not break your bank account to ride each year.

    Bill O'Neal
    WCM
    Last edited by Mr. Bill; 01-05-2010 at 03:48 PM.

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