TR2/3/3A TR3 gas tank vent

[TFB]

Can anyone tell me the tubing size for the late tr3b tank vent.I dont have bango setup for the 1/2 nf threads.I may drill and tap for a 3/8npt and run 1/4 copperX 3/8 npt compression 90,or ?
Also does vent tube attach to anything, how much does it protrude past floor grommet,and does it go anywhere under the car or just stick through the grommet a little?
Thanks
Tom?

 

[PeterK]

It might be 1/4 or 5/16, just goes through the trunk floor and hangs there. It's just a vent but when your tank is full it can also be an overflow so keep that in mind.

 

[Geo Hahn]

Mine is held by a clip (like the ones that secure the fuel line to the frame). Looks to be 5/16":

 

[Twosheds]

It might be 1/4 or 5/16, just goes through the trunk floor and hangs there. It's just a vent but when your tank is full it can also be an overflow so keep that in mind.

On hard lefthanders.

 

[TR3driver]

On hard lefthanders.

Not even all that hard, if the tank is nearly full. With 3/4 tank, I was spilling fuel just turning left from a stop sign onto a major road (45 mph, part of my daily commute to work).

My suggestion is to block the original vent entirely, and add a small hole (if there isn't one there already) to the inner plate of the gas cap. I've been running that way for many years and it works for me.

In a full service gas station (so you know it was a long time ago

) once, the attendant kept topping up the tank even after it was above the overflow. I had to yell at him to stop, as he hadn't noticed the spreading pool of gasoline under his feet.

 

[Geo Hahn]

Yep, I try to remember to not fill the tank too full but seems like someone always comes over with the 'I used to have one of those...' and I get distracted until the pump clicks off.

Then my cologne du jour is Eau de Shell.

 

[Twosheds]

Years ago my friend was following me on his '68 Triumph Bonneville. I went around a hard lefthander. When I looked in the mirror, I noticed that he had fallen far behind! He didn't drop the bike, but had a few anxious moments. He cautiously caught up, then noticed that the road only became slippery in hard lefthanders (the tank was't completly full, Randall) and stayed close unless we came to one.

 

[TFB]

Thanks for all the good info,and Geo for the pictures of clip under car.
Randall,I checked my cap,and I guess you mean drill hole in spring plate I like that idea,no hole there now(not much of the gasket left either).Seems like a little diaphram vent/check should be avaliable for similar applications.
I never thought about the overflow problem with the vent being lower than fill neck,or turn spillage.Funny I had a 61 TR3 40+ years ago and dont remember problems with spillage.Mabe never had enough money to fill the tank at 35cents a gallon.
Thanks again for all the replies,
Tom

 

[TFB]

I just saw this and lots of similar vents.Maybe I will upgrade . ven/t roll over
tom

 

[TR3driver]

He didn't drop the bike, but had a few anxious moments.

Man, I hate it when that happens! I presume you were going fast enough that he just got a lungful of fumes and maybe a few drops on his faceplate; rather than enough being on the road to make it slick.

Part of the reason I quit riding, you just never can tell when a slick spot will appear under your front wheel.

 

[TR3driver]

Randall,I checked my cap,and I guess you mean drill hole in spring plate

Here's a photo of mine. Pretty sure I didn't drill it myself, but it's possible I did and just forgot about it.

 

[TFB]

Thanks for the pic Randall.
I thought thats where you meant.
I am thinking of doing the same or going with aftermarket vent/rollover valve.

Thanks
Tom

 

[Twosheds]

Man, I hate it when that happens! I presume you were going fast enough that he just got a lungful of fumes and maybe a few drops on his faceplate; rather than enough being on the road to make it slick.

Part of the reason I quit riding, you just never can tell when a slick spot will appear under your front wheel.

He slipped, but was able to recover before going down.

Good thing, too; it is a beautiful bike, restored by my friend.

Just before we left my house: Man, that was a long time ago! Look no graybeard!