Gas cap-how to tell if it is venting??

[zenBD]

So... I know this has been covered, & I've read a bunch on it, but I think I may have a gas cap venting issue and I'd like to know how to find out...also how to fix it if it is an issue.

I noticed as I was waxing the tank after a ride today that the tank seemed to pop as if it had been "sucked in". After reading some posts, I realized that it had done some stalling that I thought was associated with not having the petcock all the way in the on position... But that may have actually been due to the gas cap. Also, the bike seemed to run like shit today... Intermittently... Possibly ever other gas fill up ( now that I think back on it).

Can you guys tell me how I can check if it is not venting properly?

Can you tell me how to fix it if it isn't?

Will any aftermarket VENTED cap fix the issue?

I believe it is the stock cap, but there is no white plastic thing under the cap...just the stainless top and a grey threaded piece with two little holes and a screw in the center.

Thanks!

 

[Sven]

1. Top off gas tank. Why? Less air gap.
2. Remove fuel line at tank.
3. Install a line from tank to gas can.
4. Turn on petcock or turn ignition key on to cycle the fuel pump [if applies].
5. Watch the flow stop or keep flowing into container.

If:
It flows, then no change as in no gas cap clogging if petcock style.
It trickles and almost stops and this is the fuel pump style, then yes, a problem.
It flows out real quick when you pop the gas cap = It's the gas cap.

How do I clean a gas cap?:

Buy bulk vinegar like at costco for 3 bucks a gallon. For a day or more, dip the gas cap in a plastic cup full of vinny so you can throw it away later. Pour the vinny in the sink and clean that too when you wash out the gas cap with hot water. Then air dry it or blow dry it out.

Rubber will swell ever so slight so remove any rubber. Do not worry about internal rubber, as long as it has a sealing effect it won't pop out like a jack in the box when swollen, meaning.

Install gas cap, top off tank, repeat the flow test.

 

[Th3InfamousI]

 

[zenBD]

1. Top off gas tank. Why? Less air gap.

2. Remove fuel line at tank.

3. Install a line from tank to gas can.

4. Turn on petcock or turn ignition key on to cycle the fuel pump [if applies].

5. Watch the flow stop or keep flowing into container.



If:

It flows, then no change as in no gas cap clogging if petcock style.

It trickles and almost stops and this is the fuel pump style, then yes, a problem.

It flows out real quick when you pop the gas cap = It's the gas cap.



How do I clean a gas cap?:



Buy bulk vinegar like at costco for 3 bucks a gallon. For a day or more, dip the gas cap in a plastic cup full of vinny so you can throw it away later. Pour the vinny in the sink and clean that too when you wash out the gas cap with hot water. Then air dry it or blow dry it out.



Rubber will swell ever so slight so remove any rubber. Do not worry about internal rubber, as long as it has a sealing effect it won't pop out like a jack in the box when swollen, meaning.



Install gas cap, top off tank, repeat the flow test.

I will definitely give this a go... Thanks very much, Sven

 

[Iman]

put the cap to your lips and blow - if you can't blow thru it its clogged

 

[zenBD]

Is it possible that the gas cap could be venting under certain conditions and not under others? Maybe how ever tight the cap was at a given time could alter how well it vents, or does that just sound ridiculous?

 

[zenBD]

put the cap to your lips and blow - if you can't blow thru it its clogged

I'll try this as well

 

[Iman]

Not likely Zen. Just blow thru it - you will be able to tell if the air is passing thru or not

 

[Th3InfamousI]

Is it possible that the gas cap could be venting under certain conditions and not under others? Maybe how ever tight the cap was at a given time could alter how well it vents, or does that just sound ridiculous?

The gas cap threads are plastic it does swell as the temperature rises. My gas cap is always noticeably more difficult to remove on a hot summer day.

 

[BBChopper]

The LAndmark cap has a double check valve that is shit. It is supposed to let gas flow down without letting it flow back up and over the tank. Take the white vent off! Dont fill your tank over the internal Bung and all will be ok.

PS I have the replacement coming R&D sux!

 

[zenBD]

The LAndmark cap has a double check valve that is shit. It is supposed to let gas flow down without letting it flow back up and over the tank. Take the white vent off! Dont fill your tank over the internal Bung and all will be ok.

White thing was gone before I got it. Anyone having them stop venting without the white thing in place?

 

[BBChopper]

White thing was gone before I got it. Anyone having them stop venting without the white thing in place?

Nope.

 

[Iman]

did you blow thru it yet?

 

[BBChopper]

did you blow thru it yet?

 

[Brew]

:roll::roll::roll::roll:

 

[zenBD]

I won't be back with the bike until Monday... Maybe later tonight if I can work it out... I'll update ASAP

 

[Sven]

By blowing in the cap only you miss:

A clogged petcock.
A kinked collapsed line.
A one hit wonder is not a full flow out the one source with 3 variables you blow into 1.

Choose your logic to troubleshooting. No manual tells you this, right?

 

[B RADDD]

i had the same problem with the bike vapor locking and shutting down,it was the cap.5 years later and still running good - fill up and never tighten cap down all the way :2thumbs:

 

[zenBD]

i had the same problem with the bike vapor locking and shutting down,it was the cap.5 years later and still running good - fill up and never tighten cap down all the way :2thumbs:

Did you have this problem with the cap w/out the white thing? Ever try a different vented cap?

 

[Marky-Marc]

I agree with Sven...if you blow through it, and it's venting fine and you still have the issue on your ride....then your cap is fine....follow his directions....

My original cap had the double venting, only my 'white' thing was of an 'OFF white' color....it started swelling...I took the 'white' vent thing out, it made it easier to unscrew when it swelled, but still vented fine. I have since then installed a new gas cap from landmark, it came without the 'white' thing....and have had no issues...full tank or not..it vents fine....and the new cap has not swelled yet....

By blowing in the cap only you miss:

A clogged petcock.
A kinked collapsed line.
A one hit wonder is not a full flow out the one source with 3 variables you blow into 1.

Choose your logic to troubleshooting. No manual tells you this, right?