Fuel Tank Vent Tube & Vacuum?

[Stig / Major Tom]

A few days after riding my scoot in the cold, I have noticed when opening my gas cap on cold days that a vacuum was present in the tank. The cap is snug to turn and I can hear the air being sucked in to the tank as I open the cap.

I am looking at that Vent Hose and wondering.
Is having a vacuum created in the tank a good thing?
 That Vent Hose runs to a charcoal canister.
Would it be a good thing to cut that Vent Hose between the fuel tank and the canister?
( I ask about cutting the vent hose  because I think I've heard the issue mentioned on other scooters. A vacuum forming which affected driveability.)
The only issue I can think of if I cut the vent hose - If the scoot goes turtle the fuel would come out. But I'm thinking if that were to happen - the fire would save me replacing all the scratched plastic when they release me from the Hospital.
The hose in question.......

[de dee]

stig stop patting the scooter you make it burp, 
   isnt the vent hose above the seal of the gas cap, cutting wont help, 

[Stig / Major Tom]

Lordy, before Turtle jumps on me....
I did find this picture of the EVAP system.
My concern is the hose they show coming from the can going to the 'throttle body'.
If I cut the line from the tank - will that screw up the 'info' going to & thru the canister to the throttle body?
In other words, if I open the gas cap while the engine is running, will that send a weird bit of vacuum info to the throttle body?

[de dee]

  try warming the gas cap it may be frozen , they are suppost to vent as you use fuel,. 

[Stig / Major Tom]

stig stop patting the scooter you make it burp, 
   isnt the vent hose above the seal of the gas cap, cutting wont help, 

Respectfully -Nope......
The vent is tiny and well down inside the tank neck. The gas cap seals above the vent.
Some SYM scooters  remove this vent hose from the canister - plug the canister where this tube was removed - and let the gas tank vent tube hang down.
Seeing this very small opening in the metal vent neck - the gas spill would be slow if I turtled the scoot.  I might lay there for some time before help noticed the flames and sent for the Men With The Blue Rubber Gloves!
I ran some nice Sear's Weed Eater line down the vent to make certain it was indeed open....and "venting"
de dee, you had me out there in the freezing garage with my daughter's Barbie flash light getting this information. Now I'm going to have a nice cuppa joe and wait for the many erudite responses to this puzzle - from this amazing forum.
Stig
Exhibit #7......

[91cavgt]

When it comes to the emmissions equipment, I would NOT recomend cutting ANY hose. 


On carbed engines, there is low pressure fuel running to the carb, and most of the time the fuel pump is not a very good one and it has to suck the fuel down the fuel hose to the fuel pump.  If there is any kind of vacuum in the fuel tank, it could cause problems. 


However, our Like 200i is not carbbed.  It is fuel injected, and the fuel pump is submerged in the fuel.  On top of that, it is a high pressure electric fuel pump.  There would have to be a MASSIVE amount of vacuum in the fuel tank to cause problems. 

Also, if you were to cut that hose, then every time you park your scooter you will have fuel fumes coming from it.  Do you park it in a garage?  It would smell like you have an open container of fuel in your garage.  That is not safe at all. 



I'm typically all about modifying a scooter for better performance, but this is an area that even I leave alone!     

[Stig / Major Tom]

I'm typically all about modifying a scooter for better performance, but this is an area that even I leave alone!     

Thanks for your reply 91-
So, do others have this vacuum in the tank after riding?
I will try bringing the fuel tank cap in and warming and drying any moisture out of it. If it is supposed to vent - it ain't doing so.
I do not think there would be any fumes to speak of - take a look at that vent opening - looks to be about 1/16th of an inch.
When the days warm up a bit I will try breaking the seal on the gas cap and running the scoot on the center stand - which would be equal to cutting the vent tube. See what happens.
Stig

[91cavgt]

Thanks for your reply 91-
So, do others have this vacuum in the tank after riding?
I will try bringing the fuel tank cap in and warming and drying any moisture out of it. If it is supposed to vent - it ain't doing so.
I do not think there would be any fumes to speak of - take a look at that vent opening - looks to be about 1/16th of an inch.
When the days warm up a bit I will try breaking the seal on the gas cap and running the scoot on the center stand - which would be equal to cutting the vent tube. See what happens.
Stig

I've never experienced what you describe on my Like.  On cars I have, but never on my Like. 

[Abner_Bjorn]

On the SYM forum there is page after page of discussion on this topic for the HD200.   Some have gone as far as removing the whole smog system.  The problem occurs when you overfill the tank and fuel runs down the breather hose into the canister, filling it with fuel.  You lose the ventelation.   The easy fix for the HD200 is to remove the line from the tank vent to the carb and plug it at the carb.  Then replace that tube with a longer one that runs behind your back side panel and away from anything hot.  The Like has a warning sticker under the seat that overfilling the tank can clog the canister and lead to problems.   I did the mod on My HD200, and can fill the tank to the very top.  I have never had a problem.  I want to do the same thing with my like.  Ask ootscoot from the SYM forum.  He is a dealer and knows both SYM and Like scooters.   

[Stig / Major Tom]

On the SYM forum there is page after page of discussion on this topic for the HD200.   Some have gone as far as removing the whole smog system.  The problem occurs when you overfill the tank and fuel runs down the breather hose into the canister, filling it with fuel.  You lose the ventelation.   The easy fix for the HD200 is to remove the line from the tank vent to the carb and plug it at the carb.  Then replace that tube with a longer one that runs behind your back side panel and away from anything hot.  The Like has a warning sticker under the seat that overfilling the tank can clog the canister and lead to problems.   I did the mod on My HD200, and can fill the tank to the very top.  I have never had a problem.  I want to do the same thing with my like.  Ask ootscoot from the SYM forum.  He is a dealer and knows both SYM and Like scooters.   

Thanks wallboard,
Yeah, I've read the  stuff regarding the HD200 (for some time now  the HD200 is my favorite  'next' scooter - so,  I freq. read up on it)
I've only noticed this "vacuum in the fuel tank" thing  a couple of time recently - in this cold weather riding.
The scoot is never over-filled - and the fuel isn't going anywhere it shouldn't -
I spoke with the tech today on the phone and he said the gas cap does have a one-way vent - it vents pressure OUT, and should not be creating a vacuum in the tank. It might be letting pressure out while running and the underseat area is warm - then slowly causing a low pressure in the tank as it sits on a cold day.
He agreed that it could cause some driveabitlity &/or fuel delivery problems on a long ride if it really is building a significant vacuum while running.
I'm going to bring the cap in, warm and dry it.
Scoot runs fine - just noticed the vacuum when fueling.
Stig