SBT Jetski Engines, Parts & Accessories

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  1. #1
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    Default 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 at 03:01 PM. Reason: add info

  2. #2
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    Default 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.

  3. #3
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    Default 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?

  4. #4
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    Default 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.

  5. #5
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    Default 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?

  6. #6
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    Default 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.

  7. #7
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    Default 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!

  8. #8
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    Default 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.

  9. #9
    Joined
    Apr 2006
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    NJ
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    Default 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?

  10. #10
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    Default 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.

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