Bonneville America Forums Forums Technical Forums General Tech Fuel overflow Non Return Valve

I have had a problem with my tank creating a vacuum. I checked the cap and that is fine, so I checked the overflow and the non return valve( located next to the air filter) is blocked.

do you need the non return valve- what purpose does it serve?- in the mean time, I have removed it and jointed the breather pipe

Thanks in advance

The vent and valve serve two different purposes.
The vent is so the tank can breathe, it actually sucks air in as the gas is used. The little check valve, controls the breathing in one direction (you should be able to blow through it one way and not the other) it is probably just a little ball bearing riding in a sleeve, so it must be upright to operate as designed. Also, by only allowing flow to come in, the gas will not escape should you fall down go boom.
You can run fine without it, but it really should be there for safety's sake. If you do not want to replace it, just get one of the vented gas caps at newspeedmaster.com. A lot of have gone that route and they also look way nicer than the stock caps.

>You can run fine without it, but it really should be there for safety's sake. If you do not want to replace it, just get one of the vented gas caps at newspeedmaster.com. A lot of have gone that route and they also look way nicer than the stock caps.

I've been thinking the same thing.
My valve works ok, but it seems this would allow for elimination of the hose.
Benefits would be minor cleanup, no concerns re: kinks, pinches, one less thing to mess with when you pull the tank.
In a word, simplify!

I would still leave the hose on. If you overfill your tank the overflow comes out the vent hole, and you don't want to end up with gas spilling underneath the tank. Bad idea, sparkie thingies and all are under there! Could go BOOM!

Gotta agree with that one. "Someone" I was riding with overfilled his tank slightly and the puddle of gas that formed under his bike would be more than enough to make a large fireball had it been draining on TOP of the engine....

The vent valve is good for checking your fast-ball technique. After screwing with vent problems I tossed the valve. The only time I've ever had gas overflow is when I've stopped for gas and parked on a hot day rather than taking care of business and then getting gas last. There were times I did this and had gas overflow from the cap and run down the tank and all over the engine.
All other things being equal, I'd rather have the gas puddle under the bike from the vent line than bubble out from under the cap and drip onto a hot engine... and then puddle under the bike.

If you want to keep it, I'd suggest you take it out and shoot some WD-40 in it and then reinstall it.

Thanks everyone for the warnings- I will now use WD-40 and return it. As I removed it from the bike, it was in the incorrect position and subsequently created the vaccum. After reading the board, I played around with it and see that it will work if placed vertically. If anyone does happen to have a photo of how it should look in position, I would be very grateful

Thanks everyone for your help so far.

Regards

RodYork

Rod,
The lighting wasn't very good but hopefully this will help.

Just curious... How's that 'Lil buger come apart?

Richard(rwright)- thanks for that...but you have me more confused now. Mine appeared to be behind the fuse box, under the seat-I could not find the hole that the holding clip fitted into- from your photo could you describe where it is!

thank you in advance

Regards

rodYork

p.s.Reid (Reido113)- I believe its a sealed unit- I ended up with petrol(Gas) and then WD-40 in my mouth as I tried to prize it open!

Mine was betwen the carbs in front of the airbox, in-line with the fuel tank vent line (as in the photo above). So after taking it out I just plugged in a short piece of plastic tube to take its place.
I don't think you can take it apart.

Rod,
I posted some better pics on webshots.


This picture was taken from the right side of the bike. The star shaped rubber up and to the left of the clip location is the airbox support. You may have to lean the bike over on the kickstand and look up behind the right side carb-to-airbox rubber to see the clip location. It should be a grommeted hole in the down tube.

Richard!!!!!!!!!

Thank you ever so much. After your 2nd photo and description I found it easily. I had been looking on the wrong side and could not for the life of me see where it went.

There used to be a puppet show in UK called Thunderbirds (35years ago) and the end credits had close up photos of parts of space rockets- which when expanded upon- look obvious as to where they would go-

This is how I felt!

I have found the intro which gives an idea what I mean and hope this is not lost in translation while going over the pond!

http://www.youtube.com/watch?v=chRbbK45eb0

Thanks once again- you solved hours of puzzling

Kind Regards

RodYork

>you don't want to end up with gas spilling underneath the tank.

Yeah.
Neglected to mention with vented cap & hose removed, stock vent would need to be capped.
I think that'd effectively be the same setup everybody ran in the past.

The valve in the vent hose is to keep gas from running out if the bike falls over. The manual claims the cap has a vent that is pulled open when there is a vacuum in the tank. If excess pressure builds up, the hose is supposed to take care of that. If the tank is overfilled, gas will run down the vent hose. A lot of gas down the hose could probably push the valve shut. When the gas evaporates, it will leave behind a sticky residue that will glue the valve closed. Sometimes, the valve just sticks on its own too.

update- 1 tank in and the bike is running fine and dandy again!

Thanks everyone for your help- job sorted!

watch out for the video!