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Gas tank pressure? Is it a problem?

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Since new i have noticed my 17' 250RR fuel tank makes a strange noise every once in a while, even when just sitting in the shop.  Sounds like its struggling to release air.  After a long hot ride yesterday, I cracked the gas cap this morning and a lot of air pressure released.  Just wondering if this is something to be concerned about?  I noticed there is a one way valve under the gas cap.  Little green part.  Any info would be appreciated on this. 

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Ours did also. Then the little green thing fell out. Didn't have that anymore. 

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5 minutes ago, ccullins said:

Ours did also. Then the little green thing fell out. Didn't have that anymore. 

So you are just running a straight line from the cap to the frame?  No valve anymore

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Correct. 

It gets a little bit of dirt collecting around it  from the fuel when the tank is totally full, but never see any gas coming out or drips. 

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Are you guys still connecting the hose to the inlet on the frame? Curious if gas got in there it would travel down to the hole that's right above the pipe and drip on it.

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If you fall often then I would worry because the gas will drain into the stem degreasing the bottom bearing then it will rust, finally a replacement is needed. Not an issue if you service it at least once a year. Inline valve is the problem with pressurizing the tank. Pressure in the tank can stall the bike, flood the bike or crack the tank. We had to stop short in a race because my 350rr overpressure the tank stalling the bike. Tank looked like a football when he finally got back to the pits. As Kran said remove the vent check ball/valve before the first ride!

Edited by weantright

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The stock hose connector into the frame doesn't go into the stem or brearings. It's mounted behind it. Yes we still use it. 

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Ah, then 'moose call' of a hot fuel tank venting pressure. All good advice above. If you drop the bike a lot, keep the one way valve on. if you do not drop the bike, a mini-breather filter is a good idea. If you hear 'the moose' carefully open the gas gap to let the pressure out. Store the bike out of the sun. Some even toss a tiny tarp (like the free ones from Harbor Freight) over the tank and seat when parked to keep both from the sun heating them up. I've near burned my butt more than once!

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