Gas spraying out of gas cap

#1
Hey guys, I put a different gas tank on a Honda clone engine I had, and when I start it up gas sprays out of the vents in the gas cap. Can anyone tell me why this would be happening?

Thanks in advance.





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#3
Gas sprays out, but it runs?

Is it really a spray?

Does it do it right off the bat, or when the engine is hot?

Does it come out on the sides of the cap, or the breather hole?
 
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#5
It does it as soon as I start it up, and it really does spray out of the breather holes in the cap, I checked to make sure the cap or any seams on the tank weren't where it was leaking. What would cause it to be pressurized?



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#7
Sounds like the fuel is sloshing around from the vibration, Look for a crack where the neck meets the tank or just a bad vent/seal on the cap itself, I don't see how the tank could pressurize unless the vent is mostly plugged, I see the tank is mostly full, try running it with less fuel..........................Tom.
 
#8
Sounds like the fuel is sloshing around from the vibration, Look for a crack where the neck meets the tank or just a bad vent/seal on the cap itself, I don't see how the tank could pressurize unless the vent is mostly plugged, I see the tank is mostly full, try running it with less fuel..........................Tom.
Less fuel, that's what I'd try.
Then again he could always drain all the fuel and see if it still spurts gas.
If it does, he might have a real money maker right there!
 
#9
Sounds like the fuel is sloshing around from the vibration, Look for a crack where the neck meets the tank or just a bad vent/seal on the cap itself, I don't see how the tank could pressurize unless the vent is mostly plugged, I see the tank is mostly full, try running it with less fuel..........................Tom.
I didn't think about the vibration. I bet that is the :thumbsup:answer.
 

markus

Well-Known Member
#10
Those fuel caps on tanks like those will usually have like 2-3 sections in the vent system to avoid fuel coming out of them Is there an almost cup or bowl looking section when you look at the underside of the cap? If you just see a gasket disc with a hole in it its problaby not goign to to cut it to keep the fuel from making its way out.

Even a good working cap may still get a little seepage on an engine mounted tank like that, My west bend will seep a little with eve a good cap (its a real shaker though) I found one of the stock cap that they used in the early days with a big bubble top to help avoid it that I am going to try:



you might want to consider tapping a nipple on the cap and running an overflow/vent tube for your situation :shrug:
 
#11
Thanks for the help everyone. I got it figured, I did exactly what Markus mentioned. The tank is from an old PowerProducts lawn mover, with only one hole in the center for a vent. I drilled that hole out to accommodate a hose spline fitting and am now running a line off of it for a breather. Gas only tries to spray out at high rpms, so I put a loop in the line and used zip ties to keep it like that and the fuel will not make the loop. Problem solved. Next time I get to local power sport shop I'm going to grab one of these little breather fittings that the mx guys use to stop gas on there breathers.


Thanks again for the help. I'll post a picture later on after work to show what exactly I did.


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#12
This is what I have for now, going to get one of those vents and change to red line, but this does do the trick.





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#16
This whole thing just seems silly and doesn't make a whole lot of sense.
Ya I don't understand,I've never had this happen before on similar tanks, but a co-worker of mine who races motocross says this is a common thing on mx bikes if they don't have one of those vents on the end of the breather line.


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#17
if you want to go the cheap route, a old used fuel filter works as a tank vent filter. I guess a new one would work too but why waste a new one? I wouldnt do it for something that needs to look nice but for a beater, absoloutly!
 
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