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  1. #1
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    Default Melted Rave Valves

    I noticed my engine was melting the plastic RAVE valve plungers that screw onto the valve stem. This was happening on my MAG cylinder. During all this, my newly installed engine suffers from a terrible mid-range bog. At WOT, it runs like a demon, the plugs afterwards are a bit light, as if it's running lean. There is a bit of tan, but it's not even.

    After my second plunger cap got melted, I had one left, and realized that it too was partially melted. It still goes on and functions, so I decided to conduct my test. Using a laser thermometer, I measured the temperature of the rave caps (the big round ones that the metal clip goes around) while the ski was running with the hose. The MAG RAVE was consistently running 10-20 degF hotter than PTO side.

    I have read up that the RAVE valve stems and the housings wear out, allowing hot exhaust gasses to get into the RAVE Valve body and melt the plastic components. I took the RAVE valves and housings out and measured the valve stem diameters. Sure enough, the MAG side was slightly thinner than the PTO. Naturally, I decided to put the MAG assembly on the PTO side and test the heat output. And what do you know, the MAG side was still hotter.

    Does this indicate that the MAG side runs leaner/hotter? Does this in any way help me identify where that terrible mid-range bogging/hesitation comes from? If my MAG side crank seal was leaking, would that not affect the PTO cylinder?

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  3. #2
    Bills86e's Avatar
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    The main cause to melting rave caps is Rave valve housing wear. If the valve/blade guide hole is the housing measure over .400" it's time to buy new ones. Also upgrade to the new green o-rings and rave valve caps. The new caps are made from glass filled nylon (6/6 nylon) These new caps will take much more heat with out melting. Also look at any wear on the valve/blade shaft itself. If its got a noticeable groove it might also need to be replaced. Also check the crank's phase or index (TDC @ 180* apart). It is pictoralized in your shop manual. That could
    affect the temperature of the engine as well as a worn wear ring affects water pressure.

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  4. #3
    Minnetonka4me's Avatar
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    I think you have an issue with the carbs as the temp difference and plugs are telling you something is up. There should be no bog.
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    Ride it like you ain't got a dime in it!!!

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  5. #4
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    i measured the housing id's and i have exactly 10mm on each (about .394") This measurement was taken with a caliper micrometer with backwards facing calipers for measuring ID's. I measured my other two spare housings, and I get the same measurement. I want to believe that they're good. The RAVE valves on the other hand vary by as much as .03". There is no noticeable groove on them, but some are thinner than others.

    I think you may be right Minnetonka4me, I believe I have a carb problem. I believe my throttle shaft is worn out, as the carbs off my new project ski are tight w/ no play at all. Perhaps I'm sucking in air right at the shaft. Since RAVES and their housings are expensive, I'm going to get this new project ski running and put the old RAVES on it, see if they heat up like on my other engine.

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  6. #5
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    Just got a new Rave Valve and a new housing from SBT. Will measure it in relation to my other Rave valves and let you guys know if it's truly that different.

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