tank vent

[jcw]

Looking for some ideas venting a DIY steel gas tank.

I have this track bike that I thought I'd try making a more track oriented tank for. I'm looking for a particular shape toward the rear and top of the tank that is better to brace and anchor my outside leg. They make add on tank pads that do the same thing. I thought maybe I'd make a tank from scratch and possibly save a few pounds too...
here's an example...
https://monkeygripp.com/pro-rider-testimonials/

Well, the tank turned out kinda hideous and not much lighter but I'm gonna finish it and the tank vent is the last thing.

Newton engineering seems to have what I want. I attached their small tank vents pdf below. Thinking of using the thv45.
If anyone has installed a tank vent and has suggestions, I'd like to hear about them before I spend money on this.

 

[gt alex]

Hi I'm doing a similar thing and have the same questions
What I have found is https://www.aliexpress.com have Harley caps with bungs and from what I can tell, most most Harley right hand threaded caps are vented.
Show us what you end up doing, Good on you giving it a go...

 

[teazer]

Simplest solution is a filler cap with breather built in. Most OEM caps are like that, so if you cut the filler cap flange out of a smashed tank and weld that in, you are probably good to go with a stock or aftermarket filler. I usually try to get a GSXR tank because there are tons of billet caps available.

Next alternative is to drill a 1/16" hole in the non-breather type cap to allow air in but it's too small for fuel to leak out.

Third is to weld/braze/solder a 1/4" hose barb on and get a one way breather valve and tube for a dirt bike. You could also wled in a bung and use a screw in barb. TZ tanks came with a one way valve that screwed on to the tank with a ball to seal them but over teh years they failed to seal, so the solution was a dirt bike breather.

fuel tank breather at DuckDuckGo

DuckDuckGo. Privacy, Simplified.

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motorcycle fuel tank breather at DuckDuckGo

DuckDuckGo. Privacy, Simplified.

duckduckgo.com

There's a ton of breathers out there.

Of go to https://www.capsnecks.com/product-category/filler-caps/

CAPS

High quality custom aluminum tanks, tank parts and accessories for any tank application.

fueltankparts.com

Fuel Filler Necks

Tanks, Inc. manufactures fuel system components and polyethylene, steel and stainless steel gas tanks for street rods and special interest vehicles.

www.tanksinc.com

Tanks - Filler Caps - Bung King Manufacturing Inc.

www.bungking.com

I welded up a tank for our RD350 drag race bike and welded on an aluminum neck and use a screw on cap that I had to drill a breather hole in. It works great. You can get steel or aluminum necks to weld on.

Simplest though is an OEM cap and "hole".

 

[jcw]

Thanks for the suggestions...

You may likely already know this-- Modern gas caps are little wonders of venting. They have tiny passages and trap doors built into them that vent the tank through the seal and into tubes that are brazed under the filler.. these tubes run straight through to the bottom of the tank to you vent hoses.

I reused the filler neck flange but welded up vent tubes since the tank was being built mostly from scratch.

As such, I can't use a screw cap vent unless I redo the filler area,, which I might just do.... it would simplify everything and I can clean up the second ugliest part of the tank.




Too bad for me about the other forum. In the end all we just want to do is share ideas and knowledge with people of like interests... how we share it is what we disagree on... that's stupid, but it's Their forum.

I come from a profession where training was hard and not all love and hugs. I was raised by a mom that didn't spare the rod. I see no issues with calling crap crap when called for but will always be willing to help with advice and whatnot when asked. I think we were all like that.

 

[teazer]

Amen to all the above. Shame about what happens when companies seeking to make revenue on adverts on enthusiast sites end up killing them off. Adnmittedly there are always some silly and rude comments that could be more helpful and noisy old farts (oops is that me?) dominating, but that's the nature of the beast. To be honest, I have heard worse language in senior staff meetings, and they don't get banned. maybe that's a trend we should start.

I have deleted quite a few bookmarks now from sites I used to spend a lot of time on. It's nice to contribute and always interesting to "hear" from others and we never stop learning as long as we are open to listen to others. This forum has some really interesting and knowledgeable members who do things I would never have thought of. And lots of newbies looking to get into old bikes. And others trying all manner of strange stuff. Good on them.

Yes, modern tanks are amazing and filler cap mods don't always work out. That's why it takes a bunch of iterations sometimes. On the Drag bike I simply drilled a small hole in the cap because it took forever to get my welding to seal properly and I couldn't face more of that adding any more bits.

I bought a non lockable screw on cap for the Phat Trakka and it has two cross drilled holes each with a ball bearing and spring under the surface to allow air in and to prevent fuel seeping out. I kept the drain hose and welded that into the bottom of the tank to let water or spilled fuel out but that doesn't connect to the vent the way the cap base is sealed. This is a variant of the one I fitted.

Keyless Motorcycle Gas Cap For Suzuki GSXR Logo Engraved Twist Off Fuel Tank Cap | eBay

Engraving: GSXR. Suzuki GSXR 600 2004-2015. Suzuki GSXR 750 2004-2015. NEW Keyless Twist Off Gas Cap with Logo Engraving. Large contoured finger. Suzuki GSXR 1000 2003-2015. Keyless Twist Off Gas Cap with Logo Engraving.

www.ebay.com

 

[jcw]

Help me understand... did u cross drill the holes and install the ball bearings and springs or did the gas cap you bought already have that? I'd totally use a vented gas cap if possible.
I agree with adding more bits getting old fast.

 

[teazer]

No. It came that way. The balls and springs were located by tiny grub screws. That is way above my pay grade..

 

[jcw]

So I looked closer at the vented aftermarket cap I have (lightech) and came to the conclusion that it should work OK.
It's a simple nonlocking screw on cap like the one teazer linked above. There is a tiny passage drilled across in the "flange" part from the filler neck side to the area between the flange and the recessed tank section where the holes were to drain water and to vent the tank. Even though I've welded shut those pipes, air can escape and enter between the recessed tank area and the outer side of the flange.
hard to describe but easier to see...

anyway, Leaked tested the tank one last time. Welded up two spots.
filled her up. and started her for the first time with the new tank. I first sat the tank on the bike outside in the sun to see if pressure would build up in the tank. Nothing. Went for a ride and cracked the tank when I got home. OK, no vacuum.
I'll check for leaks and other problems for the next week or so then decide how to paint/protect it.

Kinda a huge waste of time, but I'm glad I got my first tank under my belt.

Oh yeah, I was on a roll today so I cut the kickstand and welded in an extension so the bike doesn't fall over. The bike is lifted front and rear for the track.

 

[jcw]

Been a couple weeks and put in some miles on the tank. Everything has been working well. I am happy with the shape and function for the most part.
There is one small slow leak on the left back corner that I can't exactly identify. Fuel intermittently shows up in that corner after a long ride and sitting overnight. So, when this last tank was low, I emptied the tank of the rest of the gas, dried it out with a fan for several hours and welded the seam closed again.

As for the vent, while the small hole in the gas cap flange was working fine, I'm going to fab a little raised mounting section for the Newton engineering horizontal small tank vent.

 

[pidjones]

Your desciption of your existing vent soiunds Ok- as long as it can't suck IN rain water accumulated in the area. That would not be good.

 

[jcw]

Your desciption of your existing vent soiunds Ok- as long as it can't suck IN rain water accumulated in the area. That would not be good.

Good point. Hadn't thought about that.