Fuel Tank Vacume

Discussion in '2-Stroke Engines' started by ToyWorks, Aug 6, 2011.

  1. ToyWorks

    ToyWorks New Member

    Yet another problem. Don't they test anything in China to see if it works? My fuel stops flowing after a couple of minutes and I have to loosen the fuel tank cap to let air in and get fuel back in the carb. Are you guys drilling a hole in the cap or something so it'll breath?
     

  2. w31john

    w31john Member

    I had the same problem on my last build, so i put a very small hole in the top.No more problem with that.
     
  3. ToyWorks

    ToyWorks New Member

    Did you drill the hole in the cap itself or the tank?
     
  4. ToyWorks

    ToyWorks New Member

    I just drilled a hole in the top of the cap.....works good now, thanks a lot.
     
  5. 5-7HEAVEN

    5-7HEAVEN Member

    My Tanaka 47R engine needs to vent thru the Happy Time gas cap. I use a locking cap, so the engine vents thru its keyhole.:detective:
     
  6. The_Inventor

    The_Inventor New Member

    I have the same problem as you and I want to know what size drill bit I should use? Thanks
     
  7. ToyWorks

    ToyWorks New Member

    I drilled a 1/32" hole in the top of my fuel cap. Problem is solved now, but one should take precaution if you pressure wash or leave it in the rain you may accumulate water in the fuel tank.
     
  8. steelfan41

    steelfan41 Member

    I have the worse leaking cap imaginable. I can only fill my tank about 1/3 full or I end up wearing gas/oil. I was thinking about drilling a hole in my cap and using fuel line as a vent tube and RTVing off the vents on the cap. Does this seem like a plausible fix for my leaking tank? Open to any ideas that let me put some gas in the **** tank. I use my bike to visit my kids who live about 20m away and I hate carrying spare fuel or trying to mix at the pump. Plus they look at you funny when you pay for $1.25 in gas.
     
  9. The_Inventor

    The_Inventor New Member

    You could always just get a new cap. I dont think that they cost much and would be easier than to drill a hole and mess around with the current one and it would keep it looking nice/original
     
  10. ToyWorks

    ToyWorks New Member

    So you order a new fuel cap and find out you just wasted another 15.00 because it doesn't breath either. It took me all of 15 seconds to drill a hole and you can't really even tell it's there. Chinese suck at making anything. No pride evidently.
     
  11. The_Inventor

    The_Inventor New Member

    I dont think that drilling a hole in the cap is going to fix a seal that is letting fuel out
     
  12. steelfan41

    steelfan41 Member

    Here are a few pics of the cap. As you can see the seal is in good condition, the springs work as well. There are 4 holes in the bottom and 2 on the sides. My idea was to fill all the holes with RTV and then drill a hose to accommodate a 8-10 inch piece of fuel line to act as the vent and hopefully allow more fuel. My rides are roughly 20 miles each way and I want to be able to make a round trip w/o smelling like an oily rag. One other solution I had thought of was RTVing the underside of the seal, as right now the seal sits above the tank mouth. Would putting say 1/2 inch or 1 inch of RTV under the seal pushing the seal further down the throat fix the cap's leaking problem...:whistling: Right now I can fill up 1/3 and carry a handy liter of mixed petrol in a gatorade bottle.
     

    Attached Files:

  13. The_Inventor

    The_Inventor New Member

    What exactly are you going to hook up that fuel line vent to?
     
  14. steelfan41

    steelfan41 Member

    My thought was about 1 inch or maybe 2 in the hole I drill. Basically like the 2 stroke motorcycles run. I shouldn't (I think) run in to overflow problems. The rest of the line would be unsecured.
     
  15. The_Inventor

    The_Inventor New Member

    Where will you drill the hole is what I meant
     
  16. steelfan41

    steelfan41 Member

    Center of cap. =) Insert 1-2 inches of fuel line and add some RTV and see if it works.
     
  17. w31john

    w31john Member

    I think you need a new gas cap or your tank is bent near the seal.
     
  18. steelfan41

    steelfan41 Member

    I am trying sealant in the top of the cap above where the seal sits. I know it probably won't work however, I just have to make an easy fix attempt. Where is the best place to get a new cap if that's needed?

    Thanks, Walt
     
  19. RedBaronX

    RedBaronX Member

    I'm using a tank from a Whizzer bike, and the cap doesn't breathe on that, either. I drilled a hole, and because my bike does have to live outside during the months I ride it, I fashioned a rain "cover" out of epoxy putty, which you can kind of see here:

    [​IMG]
     
  20. steelfan41

    steelfan41 Member

    How big is that tank? I am looking for the biggest tank I can safely mount on the frame.
     
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