V7C - Fuel tank pressure normal?

[Alan L in BC]

After a pleasant afternoon on the bike, I opened the tank cap to see how much fuel was really in it (the fuel light was on) and there was a hiss of escaping pressure as it opened. I don't remember noticing this before, and since I have had the alloy trim ring, etc. off of the bike recently (corrosion that I can't explain, another question...) I wonder if perhaps I have mis-alighned something and blocked a vent?

 

[Will]

I'd check the vent under the filler cap is clear and make sure the vent hoses aren't kinked under the tank.

 

[ItalianSpiderman]

Did your bike come with the evap canister located behind the engine oil sump (like U.S. bikes)? If so, you will have two vent hoses under your gas tank; one for fuel overflow and one that leads to the evap canister. The fuel overflow hose has nothing to do with tank overpressurization, but you need to make sure the other hose, which leads to a small hole in your fuel filler neck, is unkinked. If you have no canister, then your tank vent is in your gas cap and these have been known to clog and/or fail.

To answer your question, you should not be having tank overpressurization, especially after a ride. However, I feel that the U.S. fuel vapor recovery system is probably biased towards a certain amount of tank pressure under some circumstances. It should eventually equalize out if you let the bike sit. Mysteriously, all this gear fell off my bike shortly after I bought it, so I can no longer tell you for sure!

 

[Holt]

Did your bike come with the evap canister located behind the engine oil sump (like U.S. bikes)? If so, you will have two vent hoses under your gas tank; one for fuel overflow and one that leads to the evap canister. The fuel overflow hose has nothing to do with tank overpressurization, but you need to make sure the other hose, which leads to a small hole in your fuel filler neck, is unkinked. If you have no canister, then your tank vent is in your gas cap and these have been known to clog and/or fail.

To answer your question, you should not be having tank overpressurization, especially after a ride. However, I feel that the U.S. fuel vapor recovery system is probably biased towards a certain amount of tank pressure under some circumstances. It should eventually equalize out if you let the bike sit. Mysteriously, all this gear fell off my bike shortly after I bought it, so I can no longer tell you for sure!

I can't speak for the V7C, but the Breva has two hoses, whether canister or not. The tank vent hose goes parallell with the overflow hose, and ends up in the free on EU-models. No vented cap, but the hose is likely to be twisted unless you pull it.

 

[oldmanjob]

My vent hose kinked and warped the bottom left side of my tank above cylinder head.

Black tape in picture shows the damage. Tank was replaced under warranty

 

[sign216]

My V7C occasionally does this, but not often. I wouldn't worry, unless it's every time.

If that's the case: The vent lines under the tank are often kinked by the factory, and the vent hard-line in the tank opening can also clog.

Joe

 

[Brian UK]

Another probability on those is that the little aluminium ferrule which goes through the bottom of the tank, and the breather hose fits on to, is blocked. The hole through it is very small, and should be carefully drilled out. I know my local dealer here in the UK does this as part of the PDI.