How To Replace a Vespa Fuel Line
There are some fairly common scooter projects that are actually quite simple, but can be intimidating to the novice. Replacing the fuel line is one of them. The intimidation factor can be traced to the fact that the fuel line runs under the gas tank, and through the frame up under the carb airbox.
Before You Get Started
As with every project, get all of your parts together first. Read through these directions to get a sense of what parts you may need, and then buy them. Once thing to consider is that the fuel line has to be the exact right size. Too short, and it won't reach the carb. Too long, and it will kink, and not allow the fuel to "gravity feed" to the carb. The easiest thing to do is to buy the correct fuel line from a reputable scooter dealer. Make sure to have them double check that it is the correct length.
Removing the Seat
First, you need to take off the seat by removing the three seat bolts. Then remove the two rear tank bolts.
Next, the Carb End of the Line
Next, remove the carb airbox top, then the air filter, so you have access to the carburator itself. On the carb, remove the bolt that holds the fuel banjo. Then, remove the carb air bellows. If it is in bad shape, now is a good time to get a new one.
With the banjo loose from the carb, you can pull it up and away from the carb for easy access. Remove the fuel hose clamp, and then the banjo itself. If your fuel line is old and/or crappy, you may have to cut the fuel line with a razor to get the banjo off.
Next, remove the fuel lever frame grommet. You will need to turn the fuel lever to the middle position in order to get it through the frame.
Removing the Tank
Now you get to remove the fuel tank. Pull up on the back of the tank. The Rally tanks are larger than most of the others, so you will have to manhandle it a bit to get it out on the Rally. The others are fairly easy to remove. If you are just replacing the fuel line, pull the tank up just enough to get access to the fuel tap. If you are doing both the fuel and oil, you'll want to pull the tank up further to get access to the bottom of the oil tank.
Here we see the fuel tap at the bottom of the tank. It is helpful to have a friend hold the tank, while you work on the tap. If you don't have a friend handy, use a towel to protect the frame from getting scraped by the tank. Once you have access to the tap, simply remove the old clamp and line. Then put the clamp on your new line, and attach it to the end of the fuel tap. Heating the fuel line with a heat gun helps to get it pliable and easy to slip on the end of the tap.
With the line attached at the top to the fuel tap, you need to feed it through the frame to the carb. Keep the tank out of the scooter, and loop the fuel line under the fuel control rod, and then up through the frame hole. If your scooter does not have a rubber frame grommet for the fuel line, now is the perfect time to install one.
Replacing the Tank
Then, with the tank still out of the scooter, attach a string or something similar to the end of the fuel rod. I use a very long twist tie. Feed the free end of the string through the hole in the frame for the fuel rod. This will help you guide the rod to the hole while you drop the tank back into the frame. Then gently put the tank back into place. Once the tank is back in the frame, re-install the frame grommets for the fuel control rod and the oil tank sight glass.
Then, on the carb end, feed the fuel line through the hole in the bottom of the airbox. If the grommet is missing for the fuel line on the airbox, now is the perfect time to replace it. With the fuel line inside the airbox, pull the line so you get some extra slack. Heat the end of the fuel line with a heat gun. Install the hose clamp, and then the carb banjo onto the fuel line. Re-install the banjo to the carb.
With the fuel line installed, now all that is left is to button everything up. Re-install the seat and the fuel tank bolts. First, get them all installed, but slack. Make sure the seat is in the right position by opening it and closing it. If the rear seat latch works correctly, and the seat appears to be on straight, then tighten all the bolts. Then, re-install the airbox bellows (the heat gun is also helpful here). Then, put the air filter on the carb, and the carb box top back on. You're done!