Modern Vespa

I am in the midst of figuring out the source of a recent problem with my GT and am completely disconnecting the evap system to see if it was what was at fault.

So far I have:
1. Disconnected the evap hose from the carb (of course)
2. Bypassed the evap's connection to the overflow outlet on the filler neck
3. ???

Where else does the evap system interact with the engine?

Was going to get some pics on my disconnect / finish but hopefully I can explain what was done:

(BTW...seems to have made a difference on start up doesn't seem to be as sluggish at low speed...maybe it's my imagination)

Origninally, I covered the inlet port of the carb. with a piece of nylon stocking and cinched it tight with a tie cable. Thought it might not hold on too well, hence I cut off part of the evap. tube (~ 3/4") and inserted a plastic step down adapter. Plastic tapered tip on on end and a little larger tapered tip on the other (these are used to connect fuel lines and got at West Marine retail shop).

I pushed the smaller diameter tapered end into one end of cut off evap. tube and then took a piece of foam (nothing scientifc; i.e. Particle Filtrtion Eff.) and attached it the the wider tapered tip and cinch this down with tie cable (since this end was also a step down the tie held on well). Resecured the end of the evap. tube with the original clamp onto the carb. inlet port.

To take care of the cut off evap. tube I used a cable tie to secure against pet carrier frame, and made sure that if any fuel was discharged it wouldn't come in contact with anything would ignite.

If pics needed, let me know and I'll post.

But is it only attached to the carb and the filler neck when stock?

This may help...it's in the Wiki library...

https://modernvespa.com/forum/wiki-evap

Thanks. The wiki shows how to disconnect it from the carb. I'm well past that.

I have also eliminated the evap canister from the fuel filling overflow recovery, not even mentioned in the wiki. I want to know ALL the places the evap system is connected to the scooter.

If anyone here knows fo sho, it would save me a lot of time fishing about between the frame and body of the scoot when I get time to get in there and root it out.

I think you have covered it pretty well. The overflow hose (or the one that goes from the neck of the fuel tank to the evap canister needs to be cut. I made a connection and routed the hose to the back of the scooter and down back by the license plate. Any over flow when filling will now go onto the ground behind the scooter on the left side away from the exhaust. I disconnected the hose that when from the evap canister to the carb, put a small hose at the carb end with a homemade foam filter. While this probably isn't necessary I didn't want to suck any dirt into the carb so I wanted to be on the safe side. I have cleaned the filter a couple of times and it was surprisingly dirty. I left the evap stuff on the scooter so I can easily reconnect everything if I have to at a later date. One of the bonuses is that I can really fill the fuel tank without fear of screwing up the evap canister and I have added 20 to 30 miles of range on a tank by being able to fill it right to the top now. Since I have a 2006 GT 200 and live very close to you PM me if you need anything.

Yes, you have disconnected all points where the evap system is connected to the engine.

I have disconnected four of these on Piaggio products and several on BMW motorcycles over the past eight years.

You can actually leave all the evap equipment on the scooter as long as:
1) You cut the overflow line going to the canister from the gas tank. Then, just add an extension to the line and run it towards the ground for any overflow from the top of the tank when you fill up.
2) Cut the hose that goes into the carb (or throttle body in fuel injected engines) and put a small filter where you cut it before it goes into the carb. (in a fuel injected engine, plug the hole of the hose before it goes into the throttle body with a bolt or plug and clamp it so the plug can't fall out)
That's it. Everything else is just sitting there doing nothing so you can remove it or leave it. If you leave it, you can quickly hook it up in case your state ever passed an inspection law for emissions equipment compliance. (not likely but anything is possible with politicians looking for revenue)

Michael, I did the basic evap. hose disconnect at the carb. inlet and covered inlet port to carb. with foam filter. Then took the evap. tube that was connected to the carb. and tie cabled it to the side.

Question: Is it adviseable to cut the hose from the neck of fuel tak to evap. canister? Thought that if I simply took care of the end leading to the carb. that would be it.

Note: I also remember reading another post where an MV'er removed the evap. canister ("sitting on shelf").

Sorry...but I believe sometimes "less is best"...I've had my share where I've made things a lot worse...

TB wrote: YES, cut the line and splice in a longer piece with a cheap connector and run it towards the ground for overflow.
The reason that it needs to be disconnected from the canister is that eventually, gas from the overflow line will clog the canister and it can cause pressure to build up in the gas tank.........bringing problems that you don't want to have like stalling, stumbling, etc.

As XLR8 said it is better to cut the line and run a hose out the back to the ground. I guess you really don't have to as just disconnecting the hose from the evap canister to the carb effectively disables the evap system and any adverse effects that it causes. However, whenever you overfill your tank, and despite what others may say you will overfill your tank, the overflow will go into the canister eventually. It is just a much nicer set up with the overflow hose going to the ground. I cut mine at the frame on the left side where it heads toward the front and the evap canister. I picked that spot because I added a hose clamp and secured it to the frame there, it's a nice "clean" set up, and it would be very easy to reconnect the evap canister hose if I ever chose to do so.

That is the way I elected to perform the bypass. I opted to purchase three feet of low-pressure gas line, unhooked the evap hose from the overflow outlet and ran the new gas line to the underside of the bike. It is a nice, clean look, I must say. Also be sure, if you opt to attach a foam filter to the intake on the carb, make sure it's not too dense or too packed-on since my foam job resulted in air starvation when taking off from a stop too quickly.

So, back to my post: the evap system is connected:
1. at the fuel overflow on the filler neck
2. the side of the carb
3. and where else?

There is NO where else.
See my post, five posts up from this one.

Quote:

Quote from that post: "That's it. Everything else is just sitting there doing nothing so you can remove it or leave it. If you leave it, you can quickly hook it up in case your state ever passed an inspection law for emissions equipment compliance. (not likely but anything is possible with politicians looking for revenue)"

Duh. Dunno how I missed that, but thanks for the replies. I appreciate it. Cheers.

I am so happy for this thread. Last year I disconnected the evap system on my BV200. I just disconnected the line at the carb and zip-ted the hose to another that runs along the side of the scoot. I have, on occasion too numerous than I'd like to admit, overfilled the scoot and I've had some stalling and hard starting issues reoccur. I can see gas near the top of the tank where the sending unit enters and the strong smell of gas fumes right after filling. I see after reading these well written posts that gas is most likely still backing into the charcol canister and causing these problems. To correct the problem when it occurs I take off the gas cap for about 20 minutes and all is then well. I've got to see where this line is on my scoot and also disconnect and re-route it. I'll also leave the system on the bike in case I ever need to reinstall it. Thanks for the tips!

Bob

Yep, that's your problem. Cut the overflow line and splice in another piece of 1/4 inch fuel line with a cheap connector and run it towards the ground. That will stop your hard starting and stalling issues.

Yup, put it back to rest-of-the-world specs rather than CA's ill-thought out ones (for scooters at any rate).

If you disconnected the evap hose at the carburetor that disconnects the evap system. I wouldn't think that any problems after that would not be related to the evap system with the exception of possibly filling the evap canister with fuel from an overfill and thus sealing off the tank and creating a vacuum in the tank as the fuel goes down. I'm not sure this would happen but in theory it certainly could. If that was the case I would expect the problem to be solved instantly as soon as you took the fuel cap off and released the vacuum. I would also expect to hear a rush of air when the cap is first loosened indicating a vacuum had been created. In any case, changing the line to the evap canister to an overflow line would also vent the fuel tank as well as providing an overflow route for excess fuel to outside. It sort of completes the project rather than doing just a partial fix in my opinion.

I will add - I personally do not know if the carb connection should be left open or closed - instinct says closed, as the with-EVAP condition would (with an unrestricted canister) merely create vacuum in the fuel tank.

I don't know what a normal rest-of-the-world carb has there - maybe no pipe at all.

I'm pretty sure the carb connection has to be left open. I don't think the carb will function properly if it can't draw air into the port that originally went for the carb to the evap canister. My understanding is that on Euro scooters that port is just open to the air or has a simple elbow attached that opens to the air. The whole problem arises when the carb cannot get air (or fuel vapor) from the evap canister because fuel has gotten into the canister and blocked the air/fuel vapor passage. The evap canister is one of those U.S. (or California) things that is very sound on paper but in actuality is doomed to failure. It is not unlike the vapor recovery fuel nozzles we have here in parts California. They work if the rubber shroud seals with the filler tube but that is just not possible with a Vespa fuel tank filler tube so the fuel vapors are escaping into the air when you are filling the tank anyway. The bottom line is that it is far better to dump a few drops of fuel onto the ground occasionally than to have a poor starting or poor performing scooter.

Yeah the carb has to be open. In fact I had a problem with hesitation after installing a foam filter on the end of the carb extension tube I have on the carb inlet.