Modern Vespa

What exactually does the EVAP system do on our scooters? Does it make them run better, last longer, get better mph or do they even need them at all.

It is perhaps more problematic than beneficial to most...you can do a search to review.

Then you can make a decision on whether to remove or leave alone...if you opt to remove the evaporator system...there are really two parts to consider...evaporator hose disconnect and overflow hose (there is a posting in Wiki Library for the evap hose disconnect).

You can see the link below for the disconnect of overflow hose from the filler neck (fuel tank) that goes down to the roll over flow valve or evaporator canister.

Fuel overflow hose disconnect from roll over valve (GT200)

See the link below for a diagram of the evaporation system.

Complete evap system removal?

I simply disconnected the hose that attaches from the fuel tank to the roll over valve.

But I think it would of been a smarter idea to leave the gas tank hose attached to the roll over valve, and instead disconnect the hose that connects roll over valve to the canister.

So what's the purpose of even having these on our scooters? I see alot of post where people remove them, just like the past post of you guys removing them. Why?

I know it seems they cause trouble when overflowing the tanks.

The Evap system has one purpose: To keep gas fumes from the gas tank in a closed loop so they don't release into the atmosphere. In theory, it was a good idea. Unfortunately, it can cause the engine to become hard to start, not start, run rough and stall. Even if you don't overflow the tank, many have had problems due to pressure building in the gas tank due to the fact that the system doesn't vent the gas tank properly. This is more likely to occur when the weather is hot.

If the roll-over valve fails, you could get dangerous gas tank pressure buildup. When your tank gets over-filled, it can pour into your air-filter.
You can also get vapor-lock causing starting problems.

I took the whole thing out of my 150. I made my write-up from looking mostly at 200 and 250 evap systems. They are set-up a bit different, but are mostly the same. LX150 Complete EVAP System Removal

You could just disconnect the hose from the carburetor, or you can take out the whole system.

If your worried about rolling your scooter, you can leave the roll-over valve on, just re-route the hose to the ground so you don't have gas pouring all over in your engine compartment when you over-fill your tank.

On a carburetted engine such as the GT200, the mod can be done by inserting a "T" between the carb and the overflow system. That serves both the purpose of venting the carb to the atmoshere and a drain for liquid gas that gets into the evap system. An interesting thing about modding in this way is that it allows you to restore the evap system to intended function by simpling placing a vacuum plug over the open end of the "T". After some experimentation with and without the plug, I found that the majority of problems blamed on the evap system actually have other causes.

1+ I like this idea and may go back and tweak my disconnect.

You'd still benefit by having the evap hose "disconnected" but you are correct in that it would not prevent the charcoal canister from still becoming saturated with fuel and the possible build up of pressure in the fuel tank which cause difficulty in starting engine. Might be worthwhile to consider placing "T" between the overlflow tube from the fuel inlet collar and roll over valve...or between the roll over valve and the charcoal canister...beleive either one will work. Hence, my thought is to reconnect the overflow tube to my roll over valve and then "T" in between the roll over valve and charcoal canister.

Disconnected the evap the second day of ownership.

Searched on here, read the wiki and all the threads. Seems that NOBODY on here really understands the problem. Very simple, with a simple solution, no need to remove the entire system.

Problem lies with the CV carb -- has to do with how CV carbs function -- line that connects to evap system from carb is the ONLY problem.

To prove it to yourself disconnect this line, plug the evap system end and start the bike. Alternately cover and uncover the carb end while the bike is running and note the effect on performance. Covered bike idles poorly and stalls, uncovered bike runs fine.

That's it, that's all you need to do. DISCONNECT THE CARB LINE. No need for a filter on the carb end as there is no intake vacuum present. No need to remove the full system with it's safety and environmental functions.

From this thread by Jess (owner of the MV forum): ET/GT/LX: Hard Starting, Rough Idle, or Stalling

"If you intend to leave the hose disconnected permanently, it would be prudent to affix a small foam filter to the hose inlet on the carbeurator to prevent dust or debris from entering through this hole. Under no circumstances should you completely block the inlet on the carbeurator. Another possible solution would be to leave the evaporation hose connected to the carbeurator but to fit a hose-T inline to the evaporation hose, again with a small foam filter on the end of the T to allow air to pass into the hose."

I agree with the disconnection of the Evap System to the carb...however even with this being done...if you still overfill the fuel tank the fuel can go down pass the roll over valve and saturate the charcoal canister...once this is saturated there is a build up of pressure in the fuel tank...this build up of pressure causes difficulty in turning over your engine. I encountered this when I disconnected my evap hose and then had subsequent problem starting up after a 30 minute ride...opened up the fuel cap to remove pressure and it started up...hence I disconnected the fuel line at the roll over valve.

Saturating the charcoal filter can happen if you have fuel enter and saturate the charcoal filter via the overflow tube.

I have had several occasions of pressure being release from the gas tank when opening it. I'm going to give it some time, I have'nt that I known of had many issues yet with it. But putting the "T" between the carb and the overflow system seems what I might go for in the future.

I have had this issue, but not sure if its cause of the EVAP or not

Won't start

This happens EVERYTIME I drive long distance, or on the scooter for a long period of time.

Your problem is being caused by the pressure in the tank due to the Evap not venting it enough. There have been numerous reports of this on all models that have the EVAP system. (North American Models only). We usually see more of these problems when the weather turns hot. Disconnecting the Evap will solve the problem. Maybe putting a "T" in the overflow hose will stop the pressure but it will probably need to be a large "T" because if the tank is not vented well, you'll continue to have the problem.

No, that is not correct. A "T" in the hose to the carb creates an opening in the connection between the rollover valve and the charcoal cannister. Study the diagram below. The "T" goes in the hose to the right of the carb.

Just wanted to add a note.

I was having no issues with my gt 200 starting or stalling but after 2 years or ownership and reading the posts about the evap system decided to disconnect it. I cut the hose by the carburetor put a piece of foam over the end going into the carb and plugged the end going to the canister.

The 200 ran better and my gas mileage increase by an average of 4 miles per gallon.

I recently disconnected the evap system on my 300. This time I plugged the hose going to the carb and ran the hose from the tank to the ground. ( I will probably put the rollover back in the system.)I don't know if there is any difference in performance ( it seems a little smoother) but my mileage has gone from an average of 63.5 mpg to 71 for the last 2 tanks. I don't know if I can attribute the increased mileage completely to disconnecting the evap system. A week before I did the evap system I opened the air box a little and installed a hi flo air filter. But I did not notice the increased mileage until I did the evap system mod.

mgg

No carb on your 300. I think you mean that you plugged the throttle body. Just don't want anyone to get confused and plug their carburetor.

After disconnecting the EVAP hose from the carburetor on my 2009 S150, I stuffed some air filter foam in the inlet on the carburetor and left the disconnected EVAP hose open to ground.

I noticed a decreased in gas mileage, unlike the previous poster's experience... am I supposed to plug the hose after disconnecting it?

I removed it from my GTS300, it actually made it perform better. And the gas tank does not get pressurized. And when its so much easier to un-screw the gas cap.

For the 2015 bv350 it's fuel injected. The system looks a bit different than the image above. It looks like a line comes off the fuel tank to the roll over valve to the canister to the throttle body.

Ive seen some people block off the line to the throttle body and put a filter on the fuel tank area.

Ive also see someone block off the throttle body and the fuel tank line and drill a hole in the fuel lid.

Talking to my buddy he said get a one way check valve with charcoal in it then connect the throttle body and fuel tank line with the check valve in line.

So much info out there what do you guys think. Below is a image of the setup. In the bv350 the evap takes up like 30% of the under seat storage and makes stuff under the seat smell like gas.

More pics

Additional photos

Even more photos

On the newer 3 valve 150 engine, I wonder if anyone is having the same issues. The pressure builds in my tank pushing air out when I unscrew and it back fires upon slowing down. Every other Scooter I have had had issues with the evap. This one is maybe needs a removal as well. Then I can get the European pet carrier for more room under the seat.

just get rid of it. it does nothing for you other than potentially cause headaches. it prevents tiny amounts of gasoline vapors from getting int the air, that's all.

As the gas tank on a BV350 is located much lower than on a Vespa, the evap system is even less prone to any problems than the Vespa system. In 4 years experience with a BV, the system performed as designed. I seriously doubt there is any performance benefit to disabling or removing the system. Now, if your objective is to gain a bit of room (not 30% BTW) in the underseat area......

SPEC good idea to start your own tread since this one is 7yrs old. The OP isn't even on here anymore.

Anyone remove the evap on a new 150? If so, what did you do with the existing tubing? Did you reroute so that you would have a drain to the ground should the scooter end up on it's side?

I do not care about performance or if any can come from it. I only want the lost space from under the seat and also I don't like having the gas smell under the seat.

If it makes it smell like gas then I'm pretty sure something is off or loose on your evap system. My BV250 never smelled like gas under the seat

That problem might be worth a little more troubleshooting. I never had any gasoline odor in the storage area under the seat of my BV350. I used to keep extra gear such as a light jacket and a knit pullover in there so you'd think I would have noticed.

My bv has about 800 miles on it lol.

That means nothing. Something could've come faulty from Piaggio. I've never heard of an underseat storage smelling like gas unless there's a problem.

Ya when I start up the scooter it wants to stall or it actually does stall. I read some where they had a software up date but I can't see how that could effect it that much.

My 2014 was purchased in Dec. 2013. It has the 2013 style oil filter cap. I'd bet the 2015 has the same mapping software that solved my stalling issues. It still stalls at startup, but not while running. Like it did before the mapping software update. Disconnecting the EVAP didn't solve my stalling. I removed the EVAP for space only. 30% space savings is an exaggeration

My '16 BV350's vapor system has no gas smell, the loss of space is ~15% and is there for a reason that I agree with: petrol vapor is a constituent of smog. I have no interest in adding to air pollution. That's one of the reasons that scoot's are so attractive; their small footprint. I'm off the soap box now. You're turn!

That might be your reason for a scooter but not mine.

Good on you!

ditto