2021 Vespa 300 GTS Super EVAP Removal
I have owned my '21 Vespa GTS Super 300 for about 6 months. I use it in FL and always fill it with ethanol-free gas. A few months ago I overfilled the tank (rookie mistake #1) while the bike was on the side stand (#2). I cleaned up and kept riding. The next day, the scooter started running really rough, like someone was pinching the fuel line. Shaky starts and jerky runs, check engine light also turned on and would not go out.

After a few days, I'm guessing the gas evaporated out of the EVAP and all went back to normal.

Fast forward a few months. It's 93F and I park the bike on the curb, but I could not find a shady spot. So it sat in the heat for a good 60-75 minutes. I came back to a scorching hot seat and, to my surprise, the bike would not start. Plenty of cranking, but no start. A guy on the sidewalk helps me by testing the spark plug. It was sparking just fine. We then tested the fuel line, check, it was moving fuel. Air also looked unobstructed. After each of the above, another try at starting….nothing. I remembered the articles I read on the EVAP and how they mentioned that hot weather also affected the system. So we looked for the EVAP and followed it all the way to the throttle body, trying to disconnect it. The clamp was a compression clamp and we had no luck as we shook it from side to side and pulled on it. One last attempt to start, and wouldn't you know it….vroom! Coincidence? Maybe, but highly unlikely.

It was right there and then I decided to remove the EVAP system. From all of the research I did, I came up with two options:
Option A: Simply Disconnect and Decommission
There is a great post on this that will help you. The pros is that it is simple, quick, and relatively easy to reverse. The cons is that you have a bunch of dead weight

Option B: Uninstall and Remove the EVAP

Here is how I did it:
You can read it, or watch the video

BASIC TOOLS:
10mm socket
Scissors or cutting pliers
Screwdriver (FLAT)

PARTS (bought at O'Reily's Auto Parts):
Assorted Vacuum Connectors- Dorman #47307
Hose clamps 5/16" - ⅝" (7.94mm-16mm) Master Pro
Rubber Vacuum Caps- Dorman #47396

REMOVAL OF EVAP

STEP 1: remove pet warmer to access engine compartment
STEP 2: remove 2 10mm nuts from the LEFT side of engine compartment
STEP 3: loosen rollover valve/canister bracket by pushing the now-loose screws from step 2 and pulling the assembly down towards floor.
STEP 4: cut hose feeding the rollover valve from the gas tank neck (should enter the rollover valve on the bottom)
STEP 5: loosen the rubber strap around the canister to release it from the metal bracket. You can do this by stretching the strap to create enough slack to unbuckle it.
STEP 6: follow the hose from the bottom of the canister that is opposite the hose that goes to the rollover valve. Locate 1 zip tie that is fixing it to the chassis and cut it. Continue to follow the hose until it meets the throttle body.
STEP 7: use cutting pliers to break compression clamp open and loosen the hose into the throttle body. Remove the hose to expose a bronze "nipple" into the throttle body. At this point, the EVAP assembly can be completely removed.

MODIFYING ENGINE TO WORK WITHOUT EVAP

OVERFILL DRAIN HOSE

The hose cut in STEP 4 above is where gasoline goes in case of an overfill/expansion situation.. If left at this length, the gasoline it can emit will hit the hot engine and can cause an engine fire. In order to avoid this, the hose needs to be extended so that it drains to the ground, as follows:

STEP 1: Thread a hose clamp over the cut hose and insert one end of a vacuum connector into the hose.
STEP 2: Get a length of extra hose that will reach the bottom opening of the engine compartment (I used a piece from the EVAP assembly) and attach it to the other end of the vacuum connector, using another clamp.
STEP 3: once the hoses are secure, thread the hose down to the lower opening of the engine compartment. There is another drain hose I used to attach this one to with a ziptie.

THROTTLE BODY PORT

The throttle body bronze fitting is an intake that no longer needs to be in service. It needs to be sealed tightly to maintain the pressure inside of the throttle body. NOTE: Since the 300 GTS Super is fuel injected (no carburetor), this port needs to be sealed in order for the throttle to work. Other models that are not fuel injected may require a foam filter instead of a plug.

STEP 1: find the vacuum cap that best fits the bronze "nipple". It should fit tight and be long enough to cover the piece.
STEP 2: using a clamp around the cap, secure tightly to the bronze nipple to seal the port closed.

FINISH UP:
Make sure all tools, parts, and debris are removed from the engine compartment.
Reinstall the pet carrier
Start up your Vespa.

CLOSING NOTES:
I plan to keep the parts, just in case this does not fix my issues. I did everything so that I could reassemble it if needed using new hoses and clamps.[img][/img][img][/img]
Last Updated Tue Jul 26, 2022 9:29 pm

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