Drilled hole in my gas cap (removes tank vacuum)

Discussion in '2-Stroke Engines' started by datz510, Jun 5, 2008.

  1. datz510

    datz510 Member

    I'd been having problems with my fuel cap sealing up with a full tank and getting unreliable fuel delivery to the carb.

    I took the tinyest drill bit I could find in my garage and drilled a hole in the top center of the gas cap. That completely solved the problem, and due to the way the gas cap is built, fuel does not splash out the tiny hole.

    Took it out for a 10 mile ride yesterday and its running better than ever.

  2. fastboy9

    fastboy9 Member

    I did this too and now I never get air locks at all. When I'm leaving the bike in the garage for over a week or so I always put a bit of blu tac (i think its white tac in US) over the whole to stop the petrol evaporating and leaving nothing but oil in the tank. I have noticed that around the hole you get a bit condensation from the petrol vapours so it must come out a bit.
    Last edited: Mar 13, 2009
  3. graucho

    graucho Active Member

    Diddo... works great. My cap also didnt breath. (air lock) Like datz said...tinyest bit.
  4. Weedylot

    Weedylot Member

    Tank vacuum relief

    I thought about drilling a hole in my Whizzer cap, but was wondering... is there a vented cap that fits the Whizzer tank?
  5. screaming emu

    screaming emu Member

    Tank cap breather

    The best way around this I have found is to buy a tank cap breather for a dirt bike, drill a hole just big enough to push the breather in and you're away! I do this on all my bikes and it works great. This is a good preventative measure that is usually not considered until your bike starts playing up miles away from home lol.
  6. Simon_A

    Simon_A Member

    I guess with build tolerances (almost a oxymoron with happy times) I have never had a issue. But on the weekend I saw a cap modded the way emu said, and it looks quite neat.
  7. 5-7HEAVEN

    5-7HEAVEN Guest

    :idea:Since you guys drilled the cap, why don't you make a crude fuel gauge using a stiff long wire and a "Jack-In-The Box" ball?
  8. AlexRSS8

    AlexRSS8 Member

    Hey mate, Just noticing this, i've got a mate who has a 70cc motor, when he takes the throttle up, it cuts down. such as to say when he puts it to max throttle it just dies.
    have you had the same problem caused by the Vacuum seal in the petrol tank?
  9. screaming emu

    screaming emu Member

    The 70 may need bigger carby or jetting.

    From my experience the bike usually rides with no problems, then experiences the same as running out of fuel all together, with a cough and splatter, then nothing at all. The 70 sounds like it is possibly starved of fuel/air. Depending on where the engine was purchased it may be running the same carby as the 50's which means the engine cannot run to it's full capacity being starved of fuel and possibly air particularly at top end. You could try bigger jetting or better still a bigger carby. As a suggestion Skyhawk distributors have a carby designed with bigger jetting and air flow that seem to work quite well.
  10. AlexRSS8

    AlexRSS8 Member

    yeah probably, but the problems all fixed, this guy can't stick to the same engine for more then a month or 2 max
  11. 5-7HEAVEN

    5-7HEAVEN Guest

    :idea:If you install a locking gas cap, you don't have to drill a hole in the cap.

    The cap's keyhole will vent the fuel system.
  12. happycheapskate

    happycheapskate Active Member

    Industrial weedeater tank breathers, $5

    re: crude fuel gauge. You could be risking an explosion! That is why float-type fuel guages are made of plastic.

    Also the wire could be subject to corrosion. If it vibrates in the drilled hole, it could cause static charging/sparking.
    I like your creativity though.

    I think the tiny little breathers which go on Echo or similar commercial weedwhackers' fuel tanks would fix your problem. There are replacement kits for low prices at any major Echo power equipment dealer or most weeder/yard equipment dealers.

    The kit consists of a rubber grommet, a simple small fuel line, and a barbed end mini air filter, and a fuel filter usually (for the fuel line of a weedeater).
    If you go to the shop, you can probably get just the breather filter for $5 and hose by the foot.

    You could even seal the standard cap holes with something to prevent rain contamination, if you route the hose and breather to a safe enough location. (beware of siphoning or dripping, esp onto the engine)

    Mine doesn't seem to have any tank breathing problems (2009 grubee skyhawk.) What type is air locking on you guys?

  13. GTodd

    GTodd New Member

    I have the same problem with gas cap venting. Im going to drill the cap. Older lawn mowers and other stuff had vent holes in the caps. The hole are off set for splash. The safe thing to do is a vent tub if vented properly. GT
  14. Gregoryzim

    Gregoryzim Guest

    Unfortunately not with my lockung cap. The key barrel is sealed and does not pass through to anywhere let aline the tank.
    I had to drill a hole in the cone that surrounds the key barrel and to which the tthe cap seal is fixed.

    Now the air can flow into the inside of the cone and through the hole in the cone wallbinto the tank.