X Trainer always wants to build pressure
So my wife’s X Trainer always wants to build pressure in the tank and spew out of the gas cap or vent. I removed the stock vent under the cap and installed a cheap vent and hose to see if that would get ride of the problem. No such luck. Both the stock and after market vent don’t seem to work correctly. Am I missing something here? If I test them by blowing into them they seem to work correctly. Anyone else had this issue? Thoughts?
Answers ( No )
I can’t remember but there should be an oring under the gas cap
Mine only leaks with a full tank
Same on mine… clear tube out of the cap gurgles fuel
Early XT’s had issues with the innards of the fuel cap falling off into the tank. I think the offending parts were green. This was the valve that stopped fuel going out of the breather.
The cheapo Chinese stubby valves that are similar to the one you have now are of variable quality. A lot aren’t valves, but are just an alloy cap and therefore useless at being a breather valve. If you can blow/sick both ways up the breather pipe, then throw it away as it’s not a valve. Either that or don’t fill the tank fully.
Remove valve from back of the cap alltogether. Buy a good vent tube from ktm( with ball) or normal tube that goes in the frame.
Better off with a longer length of tube , about 8 inches and loop it over the bars
A long hose that’s down past the pipe. I’ve had a tank crack on my drz because it wasn’t venting
Bryan, I am a little confused by most of these answers.
The tank vent works to allow air to enter the tank in order to compensate for fuel used. The 1-way valve prevents fuel from escaping if the bike is dropped/inverted. The vent is NOT there to allow pressure build up in the tank to escape.
My question would be, why is there a build up of pressure? It is normally either because: 1. You have filled up with cold fuel which expands as it warms, or: 2. You have filled the tank and then transported the bike to a higher altitude. The air in the tank expands and, because the tank doesn’t vent outwards, the pressure builds up and blows out wherever it can. I hope this makes sense and might help.
I noticed my gas will boil during my ride and bleed off pressure through the vent tube. (Gasoline boils at a much lower temperature than water) I can pull off my cap and see it bubbling and the vapor coming off is thick as it does this. I’m thinking it’s heat coming off the motor that does this and may be putting some heat reflective tape on the under side of the tank soon.
2015 & 2016 Xtrainers have a simple one-way vent valve in-line in the vent hose. (The internal green vent in the gas cap was introduced in 2017.) It permits air to flow into the tank only, not out. I’ve never had an issue with gas spurting out anywhere, even after 5,000’+ elevation gain after filing the tank. I’ve also never noticed a change in engine operation due to change in tank level. There’s either enough fuel in the tank to fill the carb bowl, or there isn’t. (My Lectron carb has a clear bowl so I can see the fuel level in it.)
I had problems with the cheap vent pipe, so went back to the OEM
In Australia the plastic cup that’s inside the fuel cap is removed and binned during pre delivery because it causes the issue you describe. The tank cap is supposed to breathe through the hose. So prise that piece out and your tank will not build pressure.