Author Topic: Fuel "boiling" out the tank vent 20' 300 SEF Factory  (Read 555 times)

Sfade

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Fuel "boiling" out the tank vent 20' 300 SEF Factory
« on: May 11, 2020, 06:35:02 PM »
So when I ride pretty hard the fuel evaporates out the tank vent hose, condenses on the downward through the headstock bearing nut hole and drips all over my white fender.  I usually notice the gurgling sound when I stop.  If I pull the hose out and have it straight in the air it stops gurgling and it doesn't condense into liquid.  The vent check valve is oriented correctly as to allow air to come into the tank to replace fuel being used but not allow fuel out.  So its confusing how the fumes come out and condense in the first place.  It has stained my fender pretty bad over the past few months.  Maybe line the underside of the tank with heat shield would help.  Anyone else with this issue?
2020 Sherco 300 SEF Factory
2019 KTM 250XC
2019 KTM 690 Enduro

Twerp

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Re: Fuel "boiling" out the tank vent 20' 300 SEF Factory
« Reply #1 on: May 11, 2020, 11:06:38 PM »
I rerouted my hose. I'd lose that little bearing thing and just run a straight hose.

Sfade

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Re: Fuel "boiling" out the tank vent 20' 300 SEF Factory
« Reply #2 on: May 12, 2020, 09:19:20 AM »
I will give it a try
2020 Sherco 300 SEF Factory
2019 KTM 250XC
2019 KTM 690 Enduro

Sfade

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Re: Fuel "boiling" out the tank vent 20' 300 SEF Factory
« Reply #3 on: May 20, 2020, 09:55:38 PM »
Took out the check valve...problem solved.  Rode in 90 degree heat the other day in slow technical wooded and  sandy conditions and if ever the bike was hot it was then.  No seepage down my front fender.
2020 Sherco 300 SEF Factory
2019 KTM 250XC
2019 KTM 690 Enduro

aircop

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Re: Fuel "boiling" out the tank vent 20' 300 SEF Factory
« Reply #4 on: July 21, 2020, 09:09:08 PM »
I rerouted my hose. I'd lose that little bearing thing and just run a straight hose.
  Hi - where did you re-route the hose and what is the bearing you are talking about?  Thanks for any info

alang

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Re: Fuel "boiling" out the tank vent 20' 300 SEF Factory
« Reply #5 on: July 22, 2020, 11:13:29 AM »
Most gas caps or vent hoses
Have a small plastic ball
That acts as a check valve
When the bike is dropped so
Fuel doesn't flow out vent hose.
Sometimes causes pressure
Build up in hot weather.
Most people remove the ball
If any issues occur with pressure
In fuel tank.
2017 Sherco 300 2T Factory
2016 Aprilia Tuono 1100 Factory
2019 Santa Cruz Tallboy Carbon R
Azle, Texas

Trailrider383

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Re: Fuel "boiling" out the tank vent 20' 300 SEF Factory
« Reply #6 on: July 23, 2020, 07:54:14 PM »
Took out the check valve...problem solved.  Rode in 90 degree heat the other day in slow technical wooded and  sandy conditions and if ever the bike was hot it was then.  No seepage down my front fender.

I removed the check valve on my 2020 300 SEF Factory and it solved the fuel boiling noise but it made the fender staining problem worse!

Sfade

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Re: Fuel "boiling" out the tank vent 20' 300 SEF Factory
« Reply #7 on: July 24, 2020, 10:33:22 AM »
I kept the routing the same through the headstock nut and removed the check valve and "straight-piped" it.  Odd, as it doesn't seep at all anymore.  If I lay it over full of gas some will come out, but if it's half tank or lower and I drop it gas doesn't spill.  The hose is long and comes up rather high then down which helps as natural flow check.
2020 Sherco 300 SEF Factory
2019 KTM 250XC
2019 KTM 690 Enduro

Trailrider383

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Re: Fuel "boiling" out the tank vent 20' 300 SEF Factory
« Reply #8 on: July 29, 2020, 06:08:18 PM »
This is what I invented to test.  A tiny fuel filter. I will see if it flows enough air to vent properly.



Dangermouse

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Re: Fuel "boiling" out the tank vent 20' 300 SEF Factory
« Reply #9 on: July 31, 2020, 05:33:12 PM »
I rerouted my hose. I'd lose that little bearing thing and just run a straight hose.
  Hi - where did you re-route the hose and what is the bearing you are talking about?  Thanks for any info
I placed mine down beside the RH radiator tucked behind the wiring there.
No more fender stain
2019 300 SEF Factory
2011 TE449
Admin - Sherco Riders & Owners FB group
Just an old quick trail rider having a go.
From Qld Australia 🌏

Trailrider383

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Re: Fuel "boiling" out the tank vent 20' 300 SEF Factory
« Reply #10 on: August 09, 2020, 06:15:32 PM »
This is what I invented to test.  A tiny fuel filter. I will see if it flows enough air to vent properly.

It didn't solve the problem. The fuel boils just like the stock check valve setup did. It runs fine but somehow fuel still gets through the felt filter I added and drips on the front fender. New idea: I took the front fender off and put air filter foam up into the steering stem hole. Maybe that will catch the fuel before it drips onto the fender.



« Last Edit: August 09, 2020, 06:18:15 PM by Trailrider383 »