Tank Venting Question

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Last post 01-26-2008 5:13 PM by Arizona Warrior. 10 replies.

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01-25-2008 5:03 PM

bucky685
Joined on 01-09-2006
Dubuque,IA
Posts 2,755

Tank Venting Question

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I am thinking of making my own flush mount pop up gas cap to mount to the stock tank...

The question is does the tank vent by its self with out a venting gas cap?

and do i need a venting or non venting gas cap?

01-25-2008 5:34 PM Sponsored Links

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01-25-2008 5:34 PM In reply to

AlanH
Joined on 05-06-2004
Lakeview MI USA
Posts 5,271

Re: Tank Venting Question

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EDITED:
Tim,
Yes, the cap has a built in vent. When you open the gas cap on the hinged side is a small ORANGE silicone tubular nipple that forms a flexible bridge between the gas tank and the bottom of the cap. The nipple snaps into the outer aluminum ring of the OEM part to accomplish this function.

In the enclosed url is the tank fill hole. At just past 6 o'clock above the 5PX is the vent to one of the small tubes on the left frt bottom side of tank. I suspect but am not sure that the rear dry break vents within the tank? The nipple fits over the 5PX hole and acts as a path for the fumes. At 8:00 is the overflow tube. If you install a different cap which isn't vented i would suggest you use some compressed air to evaluate the current and planned modification. That's the best i can do w/o removing my tank. [

]http://farm3.static.flickr.com/2080/1685857245_087b5a3d5d_o.jpg

The shop manual 2-44 has some tank details

Here's the Cap Vent hole:

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Filed under: Fuel Tank, Gas Cap

01-25-2008 5:36 PM In reply to

bucky685
Joined on 01-09-2006
Dubuque,IA
Posts 2,755

Re: Tank Venting Question

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This is the type of cap i am wanting to use.http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&_trkparms=tab%3DWatching&viewitem=&item=140201573399&_trksid=p3907.m32

01-25-2008 8:04 PM In reply to

AlanH
Joined on 05-06-2004
Lakeview MI USA
Posts 5,271

Re: Tank Venting Question

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Path through Cap ... So technically, could Dice be correct I have nothing more to say on this subject

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01-25-2008 8:35 PM In reply to

bucky685
Joined on 01-09-2006
Dubuque,IA
Posts 2,755

Re: Tank Venting Question

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hmm...

Now you got me wondering.. Because the ducati gas cap i have on there right now is a vented cap..

What would happen if i put a vented gas cap on there?

01-25-2008 8:40 PM In reply to

AlanH
Joined on 05-06-2004
Lakeview MI USA
Posts 5,271

Re: Tank Venting Question

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quote:
Originally posted by bucky685

hmm...

Now you got me wondering.. Because the ducati gas cap i have on there right now is a vented cap..

What would happen if i put a vented gas cap on there?

IMO, absolutely nothing.

I suspect that Yamaha does it so that the gas fumes for the CA bikes can run through the carbon canister can that is attached to the left side.

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01-25-2008 8:44 PM In reply to

bucky685
Joined on 01-09-2006
Dubuque,IA
Posts 2,755

Re: Tank Venting Question

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quote:
Originally posted by AlanH

quote:
Originally posted by bucky685

hmm...

Now you got me wondering.. Because the ducati gas cap i have on there right now is a vented cap..

What would happen if i put a vented gas cap on there?
IMO, absolutely nothing.

I suspect that Yamaha does it so that the gas fumes for the CA bikes can run through the carbon canister can that is attached to the left side.

Thanks alan..

I'm assusming that a venting cap would be better than a non venting cap... That way the pressure can be let out..

01-25-2008 9:44 PM In reply to

jabo
Joined on 02-23-2004
Isom KY USA
Posts 5,606

Re: Tank Venting Question

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If there is no type of vent in a motor cycle tank it will collapse on a hot day. When the 650 vstar first came out a lot of their tanks (Califorina models) collapsed when they had been ridden on hot days then parked. Something to do with improper venting on the cali models. I contacted them about it because I thought mine might collapse and they told me cali models only was having the problem. I took the long way around to tell you the tank must be vented in some way or problems happen.

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01-25-2008 11:31 PM In reply to

cjmahone66
Joined on 06-23-2005
Carrollton TX USA
Posts 71

Re: Tank Venting Question

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i know if i over fill my tank, gas comes out the tube that runs down the frame. this makes me think that this tube acts like a vent and any pressure would naturally push it's way out that tube as well. i dont think it would matter if you had a non vented cap, because pressure escapes elsewhere. just my guess though, anyone want to prove me wrong?

01-26-2008 10:31 AM In reply to

rxape
Joined on 04-25-2003
Tallahassee FL USA
Posts 771

Re: Tank Venting Question

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Guys, your not just venting the top tank you must also think about venting the reserve tank. If the system is not properly vented the flow of gas to your throttle bodies will be diminished if not cut off completely. (try riding around with the reserve tank dry brake unatached Same result) Yes you need a vented cap.

TRex[

]

01-26-2008 5:13 PM In reply to

Arizona Warrior
Joined on 01-28-2005
Gresham OR USA
Posts 9,325

Re: Tank Venting Question

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+1 there is no other vent to allow air into the system as the fuel level drops.

quote:
Originally posted by rxape

Guys, your not just venting the top tank you must also think about venting the reserve tank. If the system is not properly vented the flow of gas to your throttle bodies will be diminished if not cut off completely. (try riding around with the reserve tank dry brake unatached Same result) Yes you need a vented cap.

TRex[]

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