Gas tank pressurised!

5 replies to this topic
  • Lowedog

Posted April 03, 2004 - 09:13 PM


While taking a break during a ride today I noticed gas coming out of the float bowl drain hose. After making sure the screw was tight it dawned on me that the tank had built up presssure from the hot sun. I loosened the cap and a bunch of air came rushing out. The gas stopped coming out of the drain hose. First time I have noticed that.

I have one of those aftermarket cap vent valves that is billet with a one way valve in it. I thought it was just supposed to stop gas but let air out. Anyone know of a better valve out there?


  • Hamish

Posted April 03, 2004 - 09:36 PM


sometimes the stock part is the best :)


  • MN_Kevin

Posted April 04, 2004 - 02:56 AM


Your little vent IS THE EXACT PROBLEM.

This has come up numerous times since 1998. That valve did exactly what it is supposed to do >> on a tip-over, it prevents ANYTHING from coming out, be it gasoline vapor or fluid. It is a spring loaded check valve.

I don't know how much the D.O.T., Tree Huggers, etc have contibuted to this gizmo. It DOES have it's assets >> keeping fuel in the tank where it cannot ignite, instead of draining onto your leg on a tip-over.

When the tank pressurizes like this, your jetting becomes nothing short of a nightmare.

I, along w/ quite a few other TT'ers, removed ours over the years >> problem solved.

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  • WR_Dave

Posted April 04, 2004 - 04:49 AM


I personally don't like the idea of fuel spilling out onto the hot header pipe so I left the stock vent in place. I have gotten into the habit of cracking and retightening the gas cap whenever the group stops to regroup. I know this may not work for a long off-road race ,but it works for trail riding. WR Dave.

  • The_Blue_One

Posted April 04, 2004 - 06:27 AM


Try cleaning the valve. I clean mine out every few months and haven't had any issues.When i bought mine they warned me it would get clogged.

  • Lowedog

Posted April 04, 2004 - 07:30 AM


The funny thing is that not too long before that I had filled my tank apparantly too much and had gas coming out the vent cap while going over rough terrain. So this little gizmo still can let gas through if your bouncing around a lot. My bike was running fine and this happened after a long uphill so it was a combination of heat from the engine and the hot sun.

After thinking about it I have noticed a little fuel draining under my bike occasionally when I stop after riding hard. I thought it was coming from the overflows.

Unfortunatly I gave my stock tube too a friend. :) I guess I will get another one.

Thanks for the replys,


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