Fuel tank venting

[2manywings]

  Can anyone tell me if the gas cap on a 99 Interstate is vented? I bought a used tank that had to be cleaned and coated, and in the process the overflow tube got plugged shut. Is this just an overflow or is it also a means of venting the tank?

[Chrisj CMA]

 Can anyone tell me if the gas cap on a 99 Interstate is vented? I bought a used tank that had to be cleaned and coated, and in the process the overflow tube got plugged shut. Is this just an overflow or is it also a means of venting the tank?

It is a vent.  It's common to accidentally kink the hose coming off the rear nipple and it won't run like that

[The emperor has no clothes]

As Chrisj said, it's a vent. Someone here found that there is a vented cap that will fit on the Valkyrie tank. I don't recall which model it's from. Hopefully someone will chime in with it.

[Lyle Laun]

I think Mark T found the correct vented tank cap that works, hopefully he will chime in.

My old notes indicate that this one will work:
1984 Honda VF700C vented gas cap
17620-MB1-033

Regards
Lyle

[George B]

The vent is easily kinked when removing and reinstalling the fuel tank. Mine was kinked after being serviced by a dealer before I bought it. The PO never rode it again. I found out by being put at the side of the road  thinking I had a major problem when I got to a half a tank of fuel. I learned of this problem here. No need to have a vented cap. Just look at and feel that tube at the rear of the tank. Make sure it runs straight down and free of kinks to the tee and on down.

[The emperor has no clothes]

The vent is easily kinked when removing and reinstalling the fuel tank. Mine was kinked after being serviced by a dealer before I bought it. The PO never rode it again. I found out by being put at the side of the road  thinking I had a major problem when I got to a half a tank of fuel. I learned of this problem here. No need to have a vented cap. Just look at and feel that tube at the rear of the tank. Make sure it runs straight down and free of kinks to the tee and on down.

I think his is blocked inside the tank with the coating they did to mitigate the rust.

[MarkT]

You can break the seal of the gas cap with a coin, if you run into the kinked vent line problem.  I ran Deerslayer with a penny there for awhile.  On Jade I installed a vented cap from a Magna. It's a one-way vent with a check valve, if you drop the bike shouldn't leak out. I installed that because I used the OEM vent to vent the belly tank in my modified install.  So then I needed to vent the main tank at the top to get air in for both.  The Magna cap was the perfect soln.  Of course, then I needed 2 keys.  And you can't just cut the OEM key with the cap's lock pattern on one side, as the key blanks are different. So I marked the 2 keys with colored tiny wire ties.

[Harryc]

Can't you run a wire up through the vent tube on the tank to clear it?

[John Schmidt]

Can't you run a wire up through the vent tube on the tank to clear it?

Yes you can, just don't be in a hurry. The internal vent tube actually starts up near the front of the tank, I'd give it a shot of air from the rear to make sure that's the problem....plugged internally. If you get air coming inside the tank, you've either cleared it or that wasn't the problem to begin with.

[The emperor has no clothes]

Can't you run a wire up through the vent tube on the tank to clear it?

That tank coating stuff is like an epoxy. I suspect there is a fair amount in there and it is too hard.

[2manywings]

 Thanks for all of the advise. The internal vent pipe is definitely plugged. I ran a wire through the pipe on the original tank (and measured how much of it went through it ) to get an idea what a cleared pipe felt like. I actually cut an 18" length of stainless steel cable and chucked it up in a drill to try to dig my way through the hardened coating... NO LUCK! I'm going to attempt heating the wire to try to melt my way through, and if that doesn't work, I may look at drilling a small diameter hole on the bottom side of the tank directly under the highest point of the tank and weld in a length of steel brake line routed up to that high point, then run a longer length of rubber hose along the frame and down to the area where the original hose exits the bike. Or possibly drilling a small diameter hole in the top of the tank, directly in front of the gas cap and use a grommet and press fit tube similar to what is used on the coolant reservoir tank then again running a new hose down along the frame to an exit point under the rear of the bike. The tank is black, so the rubber grommet and hose wouldn't be all that noticeable. Any thoughts?

[The emperor has no clothes]

Thanks for all of the advise. The internal vent pipe is definitely plugged. I ran a wire through the pipe on the original tank (and measured how much of it went through it ) to get an idea what a cleared pipe felt like. I actually cut an 18" length of stainless steel cable and chucked it up in a drill to try to dig my way through the hardened coating... NO LUCK! I'm going to attempt heating the wire to try to melt my way through, and if that doesn't work, I may look at drilling a small diameter hole on the bottom side of the tank directly under the highest point of the tank and weld in a length of steel brake line routed up to that high point, then run a longer length of rubber hose along the frame and down to the area where the original hose exits the bike. Or possibly drilling a small diameter hole in the top of the tank, directly in front of the gas cap and use a grommet and press fit tube similar to what is used on the coolant reservoir tank then again running a new hose down along the frame to an exit point under the rear of the bike. The tank is black, so the rubber grommet and hose wouldn't be all that noticeable. Any thoughts?

Wouldn't it be a lot easier, simpler, less frought with possible problems to just go with the vented cap ?

[MarkT]

Thanks for all of the advise. The internal vent pipe is definitely plugged. I ran a wire through the pipe on the original tank (and measured how much of it went through it ) to get an idea what a cleared pipe felt like. I actually cut an 18" length of stainless steel cable and chucked it up in a drill to try to dig my way through the hardened coating... NO LUCK! I'm going to attempt heating the wire to try to melt my way through, and if that doesn't work, I may look at drilling a small diameter hole on the bottom side of the tank directly under the highest point of the tank and weld in a length of steel brake line routed up to that high point, then run a longer length of rubber hose along the frame and down to the area where the original hose exits the bike. Or possibly drilling a small diameter hole in the top of the tank, directly in front of the gas cap and use a grommet and press fit tube similar to what is used on the coolant reservoir tank then again running a new hose down along the frame to an exit point under the rear of the bike. The tank is black, so the rubber grommet and hose wouldn't be all that noticeable. Any thoughts?

The only need for the hose I'm thinkin is to provide a drain in case you fill to the top and it expands. Assuming you put the small hole in the filler cap collar to vent air in.  Which I did before I got the Magna vented cap, then plugged the drilled hole with a rivet. I don't see a need to have a drain hose provided you don't fill to the top w/o burning some out right away.  That's a procedural fix - on the road, gas up after lunch. If not then don't top it all the way up. You don't need the hole if you get a Magna vented cap.  It's identical looking and in use, to the Valk cap.  So you need 2 keys then.  Not a problem if you mark them like I did.  Or use colored enamel or nail polish.

[2manywings]

  I think your right about the Magna cap. Is it an identical replacement to the original, and for what year Magna did you use?    Thanks!

[MarkT]

I can't find the email on it.  Weird I keep everything. Anyway, it's an exact replacement with a check valve vent, different key blank.  I think all years the same.

[RGM]

Where the vent comes out of the bottom of the tank it looks like it should be hooked up to a hose. I can't see anything on my bike and parts schematics doesn't show one either.  Is there supposed to be one?

[Chrisj CMA]

Yes, a hose long enough to go down by the kickstand  with a three way connector mid way with nothing connected to the horizontal nipple for a siphon break.  Easy to make if it was lost.

[DeathWishBikerDude]

Easy fix..set a penny on the fuel tank seal
Don't ask me how I know this..great security system also.

[The emperor has no clothes]

Easy fix..set a penny on the fuel tank seal
Don't ask me how I know this..great security system also.

I would be very leery of riding a bike that would pour out gas if tipped or sloshes up and out in the corners. 

[DeathWishBikerDude]

I've been in a few wrecks,never lost a drop.

[baldo]

I put a vented cap on the eBay I/S tank I installed last year. The tank had been repaired previously, and the vent tube is compromised. I don't know if it's broken or rusted through. I used a pretty good boroscope to check the run of the tube. There's a clamp inside the tank that holds the tube, it looks like it's got a hole at that spot.

Sorry, long story short. This is the cap I used...
https://www.ebay.com/itm/Motorcycle-Gas-Fuel-Tank-Cap-Petrol-Locking-For-Honda-VF750C-VF750-VF-750-700-VT-/182774992755?hash=item2a8e3d0f73...a Made in China version.

It says it fits the Valkyrie. I do have a couple of issues with it. First, I smell gas most of the time. Second, I've had to brake heavily a couple of times right after filling, and was rewarded with gasoline on my crotch. Not cool. And I've noticed residue on the tank from overflow from filling it before it sits in the sun all day at work. I might break down and buy an OEM cap from a mid-80's Magna to see if that helps.

[Chrisj CMA]

I put a vented cap on the eBay I/S tank I installed last year. The tank had been repaired previously, and the vent tube is compromised. I don't know if it's broken or rusted through. I used a pretty good boroscope to check the run of the tube. There's a clamp inside the tank that holds the tube, it looks like it's got a hole at that spot.

Sorry, long story short. This is the cap I used...
https://www.ebay.com/itm/Motorcycle-Gas-Fuel-Tank-Cap-Petrol-Locking-For-Honda-VF750C-VF750-VF-750-700-VT-/182774992755?hash=item2a8e3d0f73...a Made in China version.

It says it fits the Valkyrie. I do have a couple of issues with it. First, I smell gas most of the time. Second, I've had to brake heavily a couple of times right after filling, and was rewarded with gasoline on my crotch. Not cool. And I've noticed residue on the tank from overflow from filling it before it sits in the sun all day at work. I might break down and buy an OEM cap from a mid-80's Magna to see if that helps.

Great balls of fire, that would really be bad

[MarkT]

Mine doesn't leak or smell.  It was a Honda P/N 17620-KR3-751, made for a Magna.  Don't know who made it, but apparently not the same source as the ebay one. Most OEM parts I buy from partzilla but couldn't find the emails on this one.