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  1. #1
    Dmon1996's Avatar
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    XXL 454 vacuum leak?

    I have a pretty new just broken in 454 that seems to have a vacuum leak. Got it running and performing fairly well, but there are constantly air bubbles in the fuel line and the engine overheats even when running full out without a shell and smoking (although it smokes mostly when turning (???)). The tank is full, and I pressurized the fuel system from the muffler line thru to the carb and there are no leaks at all. I snugged the hi speed needle housing - it was a little loose, but still an issue.

    Ideas?
    Dmon1996
    Tamiya Sherman & 3 KingTigers, HL Pershing, PIV, Bulldog, Panther, Jagdpanther, Tiger I, Mato Sherman, 21st Century 1/5 scale Stuart, Baja 5b, Frog, Bruiser, TT-01, RC10

  2. #2
    1QwkSport2.5r's Avatar
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    RE: XXL 454 vacuum leak?


    ORIGINAL: Dmon1996

    I have a pretty new just broken in 454 that seems to have a vacuum leak. Got it running and performing fairly well, but there are constantly air bubbles in the fuel line and the engine overheats even when running full out without a shell and smoking (although it smokes mostly when turning (???)). The tank is full, and I pressurized the fuel system from the muffler line thru to the carb and there are no leaks at all. I snugged the hi speed needle housing - it was a little loose, but still an issue.

    Ideas?
    What you're referring to isnt a vacuum leak, but a simple air leak. When the engine is running, the fuel tank is pressurized and not under vacuum. When there are air bubbles in the fuel there are a few things to check. First off, when you checked the tank for leaks, did you test for leaks with the tank in the truck? If so, try this again but this time (with an empty tank) pull the tank out of the truck. plug either the pressure fitting or the feed fitting and blow into the other fitting with the tank under water. With the tank under water, it will be easier to see bubbles forming. If there are no bubbles, then the tank is fine and I'd go onto the fuel lines. Just replace them. When these things are made and boxed up, there is a possibility that the fuel lines developed a crack or pinhole from sitting or from assembly. Any new vehicle I get I replace the fuel lines before I even fire the engine for the first time. Lastly, ensure you are using a good quality fuel. Old fuel or poor quality fuel will have a tendency to bubble more. These engines vibrate a lot, so the defoaming agents need to be doing their job.

    I found out with my LST2 fuel tanks (the 220cc ones) tend to touch the chassis when the 3 screws are snugged down all the way where the feed fitting to the carb is located on the tank. This is going to cause vibration problems and can be a pain to get a mixture setting to "stick". Since you should have the tank out to verify it doesnt leak, get a piece of foam tape or foam weather stripping and stick a little chunk on the bottom of the round fitting area on the tank. Dont snug the screws all the way tight and this should help. If after all of this you still have bubbles, then I suggest getting a small bottle of Armorall Original and put a small squirt into your bottle of fuel. This works very well keeping bubbles at bay. RC airplane pilots have been doing this for decades. I make my own RC fuel and this is what I use to de-bubble the fuel. This should be a last resort, though. Ensure all else I mentioned is set up properly, and that should do the trick.
    GlowHead Brotherhood #3
    Using Dynamite, Enya, Fox, Jett, K&B, SH, Super Tigre, Thunder Tiger, and Traxxas engines.


  3. #3

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    RE: XXL 454 vacuum leak?

    HELP!! my losi lst2 wont respond to my radoi anymore. it worked fine untill i charged the batteries in the truck with a new charger. now nothing happens at all. i have a jr xs3 radio. im thinking its the battery in the truck. im thinking about getting the AA battery tray back in it. any suggestions?

  4. #4
    1QwkSport2.5r's Avatar
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    RE: XXL 454 vacuum leak?


    ORIGINAL: bigben3576

    HELP!! my losi lst2 wont respond to my radoi anymore. it worked fine untill i charged the batteries in the truck with a new charger. now nothing happens at all. i have a jr xs3 radio. im thinking its the battery in the truck. im thinking about getting the AA battery tray back in it. any suggestions?
    You shouldn't hijack someone else's thread to ask a question totally off the subject.

    Make sure you didnt charge it backwards and that the battery lead is seated in the receiver along with the servo leads.
    GlowHead Brotherhood #3
    Using Dynamite, Enya, Fox, Jett, K&B, SH, Super Tigre, Thunder Tiger, and Traxxas engines.


  5. #5

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    RE: XXL 454 vacuum leak?

    Sounds to me like ,someone not only hi jacked a thread ,but charged there receiver instead of the battery...IMO


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