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Hi all
This weekend I decided to do the evap bypass
I followed the instructions in what I consider the definitive thread so that I did not have to cut the hoses but just disconnect them from the evap cannister, block the one that goes to the throttle body, and extend the one from the gas tank to avoid any gas spilling on scooter parts. How to remove or disconnect the Evap Sys. from GTS/GTV

When I was done, I thought about it and wondered.
Could I have just disconnected the overflow hose from the gas tank and blocked it off, and then ran a hose from the tank under the scooter?
That way I would not have had to deal with the crazy clips and be able to put it back to stock in seconds with no hassle. ?
Forum member supplied image with no explanatory text
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The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
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Yes, of course, it's what I did!
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@dooglas avatar
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For those following this discussion - one thing to keep in mind. That line leading back to the carb or injector from the charcoal cannister is treated differently in carbed versus FI bikes. The connection into the carb should be left open (some recommend using a small filter), while the connection to an injector (as with a GTS) should be blocked.

I always have mixed emotions about these evap system discussions. Most of those disconnecting the system have never had trouble with it, and a fair proportion of those who think the system has failed notice no improvement after it is disconnected. Can the system fail - certainly. Should it be repaired or disconnected if it does - certainly. Should everyone run out and disconnect the system just in case - I'm not convinced. I have had 8 Vespa and other Piaggio scooters with this system. I have never experienced a tank venting failure.
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Molto Verboso
Piaggio Beverly 300 ie - 2012
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I have no experience with EVAP systems. Checked out some youtube movies to understand more about it. Clear now what it should do and how it works.

The question I have is whether it makes any difference to mount it on scooters and motorcycles in general considering their negligeable share in total fuel consumption.

Anyway, my 2012 BV does not have it and our 4 cars are all diesels. I guess diesels don't need it considering the low volatility of diesel fuel.
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MP3 250 and 2 MP3 500s
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As jimc said yes. I don't know about the GTS but on an MP3 you get a sizable area back under the seat if you remove the canister. Big enough for a small tool kit or spare gas bottle.

External inline image provided by member with no explanatory text

External inline image provided by member with no explanatory text

All pics here MP3 250: Removal of the evap canister and roll over valve
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Veni, Vidi, Posti
2007 GTS
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2007 GTS
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Dooglas wrote:
For those following this discussion - one thing to keep in mind. That line leading back to the carb or injector from the charcoal cannister is treated differently in carbed versus FI bikes. The connection into the carb should be left open (some recommend using a small filter), while the connection to an injector (as with a GTS) should be blocked.

I always have mixed emotions about these evap system discussions. Most of those disconnecting the system have never had trouble with it, and a fair proportion of those who think the system has failed notice no improvement after it is disconnected. Can the system fail - certainly. Should it be repaired or disconnected if it does - certainly. Should everyone run out and disconnect the system just in case - I'm not convinced. I have had 8 Vespa and other Piaggio scooters with this system. I have never experienced a tank venting failure.
what the hell did we do BEFORE government step in and mandated this system? Wy don't lawn mowers have it or weedeaters? I don't see them on boat motors. guess government needs to mandate all those classic muscle cars and old models t's to retrofit
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There's a noticeable difference if you put your scooter away in the garage after a ride. With evap, you get the mooing sound as the fuel in the tank gets hot beside the hot engine, expands and pressurises the fuel fumes. Without evap, you get a very strong smell from those fumes. Outside in the open air you might not notice those fumes, but they are pretty strong and can't be good for any creatures to breathe.

So although I think the system is a crap design, unless you have problems with it it's probably best left alone for everyone's sake.
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jimc wrote:
Yes, of course, it's what I did!
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Veni, Vidi, Posti
2006 Vespa GT (Rocket): 2005 Vespa GT (Razzo): 2007 Vespa GT (Vanessa): 2009 Yamaha Zuma 125: 2018 Yamaha Xmax (Big Ugly), 2023 Vespa GTS300 (Ghost)
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I used this technique after Rocket stranded me several times.

It sputtered until it wouldn't run, then wouldn't restart for hours.

Once I had to push it three miles home.

Another time a mile and a half.

After disconnecting the canister it became a dependable scooter again.

The success of doing this had me repeating the process on my other two GTs.

Rocket had well over 60,000 miles on it when I did this.

Bill
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2020 piaggio liberty 150
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Dooglas wrote:
I always have mixed emotions about these evap system discussions. Most of those disconnecting the system have never had trouble with it, and a fair proportion of those who think the system has failed notice no improvement after it is disconnected. Can the system fail - certainly. Should it be repaired or disconnected if it does - certainly. Should everyone run out and disconnect the system just in case - I'm not convinced. I have had 8 Vespa and other Piaggio scooters with this system. I have never experienced a tank venting failure.
What about in my case going through replacing lines just because they are 15 years old, should I keep everything stock or is there an acceptable alternative that is simpler? Carbureted May 2006 manufacture date bv 250, everything works good. It's not that much to just replace all the lines and clamps but should I even bother? One less thing to wear out and it is enough of a beater scooter that it doesn't matter if I am not keeping it perfectly stock...

What setup is simplest, cleanest and most reliable while still not being a gross polluter?
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Veni, Vidi, Posti
2007 GTS
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UTC quote
skids wrote:
What about in my case going through replacing lines just because they are 15 years old, should I keep everything stock or is there an acceptable alternative that is simpler? Carbureted May 2006 manufacture date bv 250, everything works good. It's not that much to just replace all the lines and clamps but should I even bother? One less thing to wear out and it is enough of a beater scooter that it doesn't matter if I am not keeping it perfectly stock...

What setup is simplest, cleanest and most reliable while still not being a gross polluter?
have you seen the evap systems they use on the airplanes? or the cruise ships? or the locomotives? what about the ones on those 18 wheel thingys?
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I get what you are talking about...it would be nice to set it up like a Euro bike since I am going through it I guess, eliminate anything that might wear out or cause problems if it is not really necessary.

From what I understand the Euro bikes did not have any of that. I am sure it was properly vented, and that it worked but they just had to do it differently for the united states.
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So as I am going through my 2006 piaggio bv 250 cheap maintenance deprived scooter I realize it needs a new hose from the airbox to the carburetor.

I found one at AF1 and it's only $28 plus shipping but its back ordered for 6-8 weeks which I assume is probably optimistic...

So I am curious if anyone knows what the setup is for a filter sock like you might see on a dirtbike? Eliminating airbox completely and just putting a filter sock on the end of the carb.

I would have to run the head breather to a catch can in the pet carrier which is not a bad thing as it lets you see if you are pushing oil out of the head and how much.

Would I have to eliminate the evap system to do that? I know I have to vent the gas tank, and it seems to me that venting it to the canister is no more problematic than just letting it go into the atmosphere.

I just need to figure out how to hook it up correctly, and I am guessing that the cannister runs to the carb under a vacuum? In other words the gas tank is vented to the cannister and then when the bike is running a vacuum hose from the carb pulls the fumes into the carb from the cannister to be burned rather than just all willy nilly free release into the atmosphere right?

So in the stock system there is a check valve on the gas tank vent line as it goes to the cannister. Is this the part that causes the problems?

What I am trying to do here, and why I am asking for help is to simplify the vent/cannister system and make it as bulletproof as possible and still have the fumes from the gas tank not released to the atmosphere, and be drawn into the carb when engine is running and the system is under a vacuum.

Interestingly enough on my carbed bike the fuel pump is vacuum powered. Simple and maybe while not bullet proof certainly very reliable until worn out.

Any other threads anyone remember reading about that might have some more information, or any other input greatly appreciated!
@dooglas avatar
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GTS 300ABS, Buddy 125, Buddy Kick 125
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@dooglas avatar
GTS 300ABS, Buddy 125, Buddy Kick 125
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Location: Oregon City, OR
UTC quote
old as dirt wrote:
have you seen the evap systems they use on the airplanes? or the cruise ships? or the locomotives? what about the ones on those 18 wheel thingys?
I take it you know that all those "thingys" you mentioned run on kerosene or diesel which have fairly low volatility, unlike gasoline.
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