Author Topic: what is this tube coming out of the gas tank going in to the triple tree? (Read 8366 times)

xsmooth69x · « **on:** October 31, 2011, 10:02:50 PM »

what is this tube coming out of the gas tank going in to the triple tree?

caluser2000 · « **Reply #1 on:** October 31, 2011, 10:07:41 PM »

It's just a tank breather. Without it a vacuum would be created in the tank reducing fuel flow to the carbs.

xsmooth69x · « **Reply #2 on:** October 31, 2011, 10:09:43 PM »

Quote from: caluser2000 on October 31, 2011, 10:07:41 PM

It's just a tank breather. Without it would be a vacuum would be created reducing fuel flow to the carbs.

so since i put on a fresh gas cap gasket should i pop open my gas cap when i wanna go super fasttttttttttttttttt (jk that would be a horrible idea)

so why doesn't all of our bikes have this?

HondaMan · « **Reply #3 on:** October 31, 2011, 10:09:58 PM »

Tank vent. Some of the bikes had a little trouble with the tanks draining as designed, and the vent reliefs in the caps didn't work out as well as hoped. In UK especially, those are a more common sight than here in the US. The CB125S and the higher performance CB125 twin and 175 twin had those, here, in the 1960s and early 1970s.

xsmooth69x · « **Reply #4 on:** October 31, 2011, 10:11:19 PM »

Quote from: HondaMan on October 31, 2011, 10:09:58 PM

Tank vent. Some of the bikes had a little trouble with the tanks draining as designed, and the vent reliefs in the caps didn't work out as well as hoped. In UK especially, those are a more common sight than here in the US. The CB125S and the higher performance CB125 twin and 175 twin had those, here, in the 1960s and early 1970s.

so should i put one on my 550 and 750?

Retro Rocket · « **Reply #5 on:** October 31, 2011, 10:12:42 PM »

Quote from: xsmooth69x on October 31, 2011, 10:11:19 PM

Quote from: HondaMan on October 31, 2011, 10:09:58 PM
Tank vent. Some of the bikes had a little trouble with the tanks draining as designed, and the vent reliefs in the caps didn't work out as well as hoped. In UK especially, those are a more common sight than here in the US. The CB125S and the higher performance CB125 twin and 175 twin had those, here, in the 1960s and early 1970s.

so should i put one on my 550 and 750?

They already have one in the cap.....

caluser2000 · « **Reply #6 on:** October 31, 2011, 10:13:08 PM »

Quote from: xsmooth69x on October 31, 2011, 10:09:43 PM

Quote from: caluser2000 on October 31, 2011, 10:07:41 PM
It's just a tank breather. Without it would be a vacuum would be created reducing fuel flow to the carbs.

so since i put on a fresh gas cap gasket should i pop open my gas cap when i wanna go super fasttttttttttttttttt (jk that would be a horrible idea)

so why doesn't all of our bikes have this?

There are small vent holes on OEM gas caps-BELIEVE IT OR NOT!

xsmooth69x · « **Reply #7 on:** October 31, 2011, 10:22:32 PM »

what?!?!?! seriously......

im going to have to take a closer look at this tomorrow

Retro Rocket · « **Reply #8 on:** October 31, 2011, 10:33:39 PM »

Bike wouldn't run without one.....

xsmooth69x · « **Reply #9 on:** October 31, 2011, 10:34:32 PM »

Quote from: Retro Rocket on October 31, 2011, 10:33:39 PM

Bike wouldn't run without one.....

but would it run better with a tube?

caluser2000 · « **Reply #10 on:** October 31, 2011, 10:57:10 PM »

Quote from: xsmooth69x on October 31, 2011, 10:34:32 PM

Quote from: Retro Rocket on October 31, 2011, 10:33:39 PM
Bike wouldn't run without one.....

but would it run better with a tube?

No.

xsmooth69x · « **Reply #11 on:** October 31, 2011, 11:31:11 PM »

Rigid · « **Reply #12 on:** November 01, 2011, 02:31:43 AM »

I thought those were for the rider to blow into under hard accel to increase the air pressure above the fuel for better flow? I better tell my neighbor to quit doing that. You can also pop it off the stem and rotate it up for good tank venting while riding under water. One last use would be to refill the gas tank while riding along side another vehicle with a hose.

malcolmgb · « **Reply #13 on:** November 01, 2011, 04:31:03 AM »

It is yet another 'cafe racer' mod

compliment it with a large bore pipe from the cylinder head breather to the rear damper and finish off with a taped on small container to catch the oil fumes. Back in the 60's we didn't use the container it looked better to have a small trail of blue smoke from our worn engine blowing behind us.

MCRider · « **Reply #14 on:** November 01, 2011, 07:44:06 AM »

XSSmooth: If you open the stock flip up cap on our CBs and study it a bit, you'll realize how the venting works. It occurs underneath the overhang of the cap around the tank ridge.

I can't see any need for a better system. But if you change tanks and use a different cap, you'll need to be sure it vents, like with that gaudy tube.

How would you use a tank bag?

BeSeeingYou · « **Reply #15 on:** November 01, 2011, 08:34:17 AM »

Ugly hipster fashion statement.

Don R · « **Reply #16 on:** November 01, 2011, 10:57:55 AM »

If you have a full tank and lay it over, the downward vent may trap the fuel rather than letting it ooze out the cap vent. Maybe, or not. My race car has to have a vent tube turning downward to the bottom of the tank so if it goes upside down the fuel may stay in the tank. Problem is if it lands on it's side. There is an overflow design that cancels this out too.

Toxic · « **Reply #17 on:** November 01, 2011, 11:34:47 AM »

If you instal one of those flush mount gas fillers that look like something off of a modern sport bike, then you need one to vent the tank as mentioned above. But to put it on a stock tank that already has a vented gas cap is 100% poser.

TwoTired · « **Reply #18 on:** November 01, 2011, 11:52:07 AM »

Quote from: Toxic on November 01, 2011, 11:34:47 AM

If you instal one of those flush mount gas fillers that look like something off of a modern sport bike, then you need one to vent the tank as mentioned above. But to put it on a stock tank that already has a vented gas cap is 100% poser.

What if it has that highly attractive header wrap tape on it?

xsmooth69x · « **Reply #19 on:** November 01, 2011, 11:56:21 AM »

im not modding my bike to have that i was just curious..... i dont want my super sexy cb to look like an atv or a dirt bike.

i just thought it was interesting looking

malcolmgb · « **Reply #20 on:** November 01, 2011, 04:52:02 PM »

http://forums.sohc4.net/index.php?topic=27902.750 <- a picture posted tonight.
Take a look at Hailwoods BSA Rocket3 to see a real life engine breather exiting at the rear of a bike, as mentioned in my earlier post.

754 · « **Reply #21 on:** November 01, 2011, 07:12:14 PM »

On a custom tank you may end up running a screw cap, iIhave some I built for Laverdas that I will use.
If you do the hose type properly, it can hold the gas cap while you fuel up!
I know of another trick for a billet cap that will vent it without the hose.. real simple

HondaMan · « **Reply #22 on:** November 02, 2011, 11:22:15 PM »

Quote from: Rigid on November 01, 2011, 02:31:43 AM

I thought those were for the rider to blow into under hard accel to increase the air pressure above the fuel for better flow? I better tell my neighbor to quit doing that. You can also pop it off the stem and rotate it up for good tank venting while riding under water. One last use would be to refill the gas tank while riding along side another vehicle with a hose.

Yeah, the blowing part is for the drag racer who wants to restore his float bowl levels halfway down the track, when the drain can't keep up.

xsmooth69x · « **Reply #23 on:** November 03, 2011, 12:53:58 AM »

Quote from: HondaMan on November 02, 2011, 11:22:15 PM

Quote from: Rigid on November 01, 2011, 02:31:43 AM
I thought those were for the rider to blow into under hard accel to increase the air pressure above the fuel for better flow? I better tell my neighbor to quit doing that. You can also pop it off the stem and rotate it up for good tank venting while riding under water. One last use would be to refill the gas tank while riding along side another vehicle with a hose.

Yeah, the blowing part is for the drag racer who wants to restore his float bowl levels halfway down the track, when the drain can't keep up.

no way they didnt actually blow into the tube did they?

--------------------

on that super vintage race bike why would they route that breather all the way around the motor and frame out the back? why didnt they just do the thing in the original picture and put it in the triple tree?

Retro Rocket · « **Reply #24 on:** November 03, 2011, 03:36:44 AM »

NO

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Author Topic: what is this tube coming out of the gas tank going in to the triple tree? (Read 8366 times)