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  • #1

    Breaking RAVE valves, melting RAVE caps

    I have a Challenger 1800 with dual 110 SBT motors that have always run premix. Recently I have had two broken RAVE valves on the Port side motor causing them to fall into cylinder and having to warranty the motor. I rebuilt the carbs (SBT kits) before either of the motors were put in. I am wondering since the plastic caps are also melting I may be running too lean. However my plugs show no sign of this. They are black and oily. Recently I also noticed my carbs are filling up with gas after sitting. Does this indicate leaking needles/seats? Can too rich cause RAVE problems? Does screwing the mixture screws out cause extra fuel or air to be added to cylinder? I am afraid to go out on the water again until I figure this out. Can I remove the RAVE valve and block it off with a plate until I get this straightened out? Can i ask any more questions? Thanks I am desperate to get this fixed!
    Last edited by rykohl; 04-29-2006, 02:01 PM. Reason: add info
    Tags: None
  • #2
    Re: Breaking RAVE valves, melting RAVE caps

    You have several problems.

    Yes you have leaking needle and seats or your pop-off is not adjusted correctly. Yes most likely you are running lean, possibly because of the carb rebuilds, possibly because of an obstruction in the fuel system, air leak, etc. What is your current compression on the motors? RAVE valves can not be blocked off, nor do they break, they get broken. Turning mixture screws out make it rich, and no, rich does not break anything.
    SBT Tech Support is here to help with your problems.
    We try to answer each question quickly and accurately.
    Please do not use Private Messaging for Tech Support, use the forums.

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    • #3
      Re: Breaking RAVE valves, melting RAVE caps

      This is a brand new motor from SBT. It has two hours on it, I would assume it has full compression still. I can check if necessary. After two hours the plastic that screws on to the RAVE valve is stripped, although not melted. The valve was just sitting there. I am afraid that it might break again. The insulators on the plugs are black but the rims seem to be clean. I adjusted this carb the same as the starboard motor and have never had a problem with the starboard motor. Altho that may mean nothing. I wanted to take out the RAVE since the cap is stripped and make an aluminum plate to go under the housing to block the cylinder gasses while I am trying to adjust the carb. I know the curve will be off but I dont think it will do any damage. Is the top screw that you can see the high speed? Or is it the one with the T-handle underneath?

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      • #4
        Re: Breaking RAVE valves, melting RAVE caps

        It may be worth noting that both RAVE valves broke and dropped after coming off 3/4 throttle down to idle.

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        • #5
          Re: Breaking RAVE valves, melting RAVE caps

          One last thing, if I am running lean enough to overheat RAVE valves to the point of breaking, why have I never seized a motor?

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          • #6
            Re: Breaking RAVE valves, melting RAVE caps

            I want your compression to see if you have done damage. It's possible to be lean enough to melt the raves and not seize. As I said, you cannot remove the RAVE, it will not run correctly at all. What caused your original motor to blow and what repairs were made?
            SBT Tech Support is here to help with your problems.
            We try to answer each question quickly and accurately.
            Please do not use Private Messaging for Tech Support, use the forums.

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            • #7
              Re: Breaking RAVE valves, melting RAVE caps

              I got the boat because the previous owner didnt winterize it and the blocks cracked. Had to replace the carbs with a used set since he let it sit too long. I got 2 new SBT's and they ran great for months. All of a sudden at the end of the season the RAVE valve on the left engine broke and dropped into the cylinder. The cap was melted also. The leaking needle valve is a new thing recently. What do you recommend to troubleshoot carbs to see if they have an air leak, etc? I will check compression for you tomorrow. Thanks!

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              • #8
                Re: Breaking RAVE valves, melting RAVE caps

                You need a pop-off pressure gauge or you need to take them to a shop that can properly rebuild them.
                SBT Tech Support is here to help with your problems.
                We try to answer each question quickly and accurately.
                Please do not use Private Messaging for Tech Support, use the forums.

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                • #9
                  Re: Breaking RAVE valves, melting RAVE caps

                  Perfect compression on left motor with RAVE issue, 165 both cylinders. RAVE piston not melted yet, just threads seemed to be stripped. Guess this could be the first signs of melting? Will running it that way until I get everything adjusted right cause any damage with the RAVE valve not being pulled up by the bellows? Also is it possible this could be ignition timing causing it to run hot?

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                  • #10
                    Re: Breaking RAVE valves, melting RAVE caps

                    Stop running it until you fix the problems. No, rave issues have no bearing on ignition.
                    SBT Tech Support is here to help with your problems.
                    We try to answer each question quickly and accurately.
                    Please do not use Private Messaging for Tech Support, use the forums.

                    Comment

                    • #11
                      Re: Breaking RAVE valves, melting RAVE caps

                      If the rave valve pod that bolts to the clyinder has too much wear it can cause this problem.
                      Bill O'Neal <br>
                      WCM
                      <a href="http://www.watercraftmagic.com"

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                      • #12
                        Re: Breaking RAVE valves, melting RAVE caps

                        Thanks for the response Bill. I am really stumped.....

                        I have a very accurate laser/infrared thermometer and am trying to determine if the cylinder with the slightly melted threads on the RAVE is running hotter than the others. It appears that the RAVE valve piston (MAG) is 30 degrees hotter than the other RAVE piston (MAG) on the other motor which I have never had issues with. Interesting to note that the spark plug base was consistent at 100 degrees at the base on all 4 cylinders. I would imagine if the RAVE was hotter on that cylinder than the plug temp would be higher too based on combustion chamber temp? I tried richening the mixture on that cylinder but it didnt seem to bring the temp down. The only thing I can think of now is blow by heating up the piston and melting it. I would assume tho since this is a new motor from SBT that they would have used new valves and housings so this shouldnt be an issue?

                        Next step is to swap a known good RAVE assy from my other motor to that cylinder. If the temp is still high and the cap melts I guess it wouldnt be blow by from the housing but maybe the cylinder casting?

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                        • #13
                          Re: Breaking RAVE valves, melting RAVE caps

                          We reuse housings and valves when they are good, it is very rare to have them worn, and virtually impossible to have two on the same engine. We can certainly send you two new assemblies if you wish, just call in to warranty. 877 330 0231
                          SBT Tech Support is here to help with your problems.
                          We try to answer each question quickly and accurately.
                          Please do not use Private Messaging for Tech Support, use the forums.

                          Comment

                          • #14
                            Re: Breaking RAVE valves, melting RAVE caps

                            I actually had one in here once that melted rave valve cap on one of the two clyinders. Nothing fixed it until I replaced the complete clyinder. After that, no problem.
                            Bill O'Neal <br>
                            WCM
                            <a href="http://www.watercraftmagic.com"

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                            • #15
                              Re: Breaking RAVE valves, melting RAVE caps

                              I've seen that too, but never two on the same engine.
                              SBT Tech Support is here to help with your problems.
                              We try to answer each question quickly and accurately.
                              Please do not use Private Messaging for Tech Support, use the forums.

                              Comment

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