TWM Quick Action CNC Gas Cap - Pressure build up after install

Hello, All!

I recently installed a new TWM quick action gas cap on my 2024 Panigale V4. The bike is brand new with just 30 miles on it. The problem I am running into after installing it (I have taken it off then put it back on a few times to make sure it was installed perfectly) is that pressure is immediately building up. To test this, I ran the bike idle for just a few minutes. After opening the cap, I could hear a bit of air shooting out. I also can simply sit on the bike cold, shake it a bit, open the gas cap and air would still shoot out. I’m guessing this is a common occurrence/ issue with these gas caps? I’m just worried how high the gas cap will be blown into the sky after riding it hot for over an hour!

I had a 2019 Panigale V4 prior that started having this same issue with the stock gas cap. Only difference is it turned out to be an issue with the charcoal canister. There is no way I am having that issue already as I havn’t even put any gas in the bike myself yet (please correct me if that is irrelevant). Any input on this would be great

Thanks

I think the overfilled the gas tank equals flooded the EVAP canister is pure nonsense. I think the EVAP canisters get filled with gas from all of the pressurized vapor condensing back into a liquid.

I went to a CNC Racing gas cap after a EVAP delete with my Akra full system install. I only bought the CNC cap because it fits a ripper gas can nozzle. No complaints, not vapor build up etc.

It doesn't take a lot for gas to build pressure, and I'm not sure just opening the cap and having some pressure vent out is end of the world. Just something to be mindful up. If it's causing a running problem, like the bike is getting vapor locked, then that's something to consider.

bp_SFV4 said:

I think the overfilled the gas tank equals flooded the EVAP canister is pure nonsense. I think the EVAP canisters get filled with gas from all of the pressurized vapor condensing back into a liquid.

I went to a CNC Racing gas cap after a EVAP delete with my Akra full system install. I only bought the CNC cap because it fits a ripper gas can nozzle. No complaints, not vapor build up etc.

It doesn't take a lot for gas to build pressure, and I'm not sure just opening the cap and having some pressure vent out is end of the world. Just something to be mindful up. If it's causing a running problem, like the bike is getting vapor locked, then that's something to consider.

Click to expand...

I think you may be right from what you said in your first paragraph. Makes a bit more sense!

Ya, I guess I’ll just ride it a bit this weekend and see how it goes. It just worries me how much pressure is already building up in such a short amount of time that I cant imagine how bad its going to be after running for an hour in 80+ degree weather!

The boiling temp of gas isn't that high, and of course depends on altitude. Verify something is an actual problem before seeking solutions.

I got Ducati performance cap installed and during the install I believe a protective ring was removed to allow build up of pressure in the gas tank rather than the canister. As I got told, there were cases when EVAP canister overfilled on track and fuel started to leak from hoses and people got disqualified from the races for that.
(That's rough explanation from what I got told a while ago)

panibadboy said:

protective ring

Click to expand...

???

bp_SFV4 said:

???

Click to expand...

I have no idea whats the right name, but I will find out. Mechanic did all the work

Not a mechanic…

I think you mean the pressure relief valve under the cap which is a small ball bearing there was a recall update to remove it.

andyb said:

Not a mechanic…

Click to expand...

Unfortunately the logistics of owning a motorbike in CH and attending events in EU is horrible, hence I keep it elsewhere and don't really have a way to work on the bike myself.

panibadboy said:

Unfortunately the logistics of owning a motorbike in CH and attending events in EU is horrible, hence I keep it elsewhere and don't really have a way to work on the bike myself.

Click to expand...

Swiss should join the EU then you wouldn’t have these problems

Are the vent hoses kinked? There's 2 ports on the front left of the tank. The forward one relieves tank pressure/routes to evap canister. If you still have the canister installed, the servo valve that routes the evap canister air back to the secondary air ports at the cylinders, could be stuck close.

You can have the bike sitting in the sun and enough pressure will build up to hear the vent, pressure builds up very easily in the tank. It's not fuel expansion but just the air warming

panibadboy said:

Unfortunately the logistics of owning a motorbike in CH and attending events in EU is horrible, hence I keep it elsewhere and don't really have a way to work on the bike myself.

Click to expand...

Doesn’t a carnet last for a year? This sounds more like tax evasion than customs issues

Nice.

SuperDomestique said:

Doesn’t a carnet last for a year? This sounds more like tax evasion than customs issues

Click to expand...

carnet unfortunately means you waste 1-3hrs going through customs in busy summer periods, each way.

panibadboy said:

carnet unfortunately means you waste 1-3hrs going through customs in busy summer periods, each way.

Click to expand...

Gotta pay to play. This is one of the benefits of being a part of the EU.