I changed the category, as I believe this is a Moto Guzzi Eldorado?
See the link for clues in removing the tank. Videos as well.
there is a text file in this thread that will give you an idea
It goes without saying that you don't want your tank full of gas to do this because it's HEAVY and BULKY to move.
Remove the parts I list here and you will safely and securely be able to remove and replace the tank without causing any damage to other parts of your motorcycle.
To properly remove the tank, do the following:
1. Remove the beauty cover from the lower part of the fuel tank. There are 4 screws which hold this in place. 2 are on each side of the bike. After removing the screws, lift off the beauty cover and set it safely aside.
2. Remove the air deflectors from each side of the bike. There are 2 screws holding this part in place; 1 upper and 1 lower.
3. Remove the side panels. There are 3 connectors you must remove. One in the front of the motorcycle under the lights, 1 at the bottom of the side panel, and 1 at the rear of the side panel.
4. Time to disconnect the hoses from the tank. The hose on the left, is the drain from the filler neck in the fuel bung. It's what carries spilt gas out of the filler neck and sends it out the back of the motorcycle via a drain. It is simply held on by compression and can easily be popped off. The center shows the fuel pump electrical connector. Again, gently, lift up on the locking tab catch and remove this plug. The hose on the right with the clamp, is the principal venting hose. With a pair of dykes, gently squeeze the connector together and it will spring open. You can then remove the hose from the tank.
The connector in the lower center, is the pressurized fuel line that so many people seem to break. DON'T PANIC. If you do exactly as I tell you, it will come off so easily and will not even get close to breaking. There is no need to relieve the pressure in the line. It's not that much. The secret of how to remove this connector is so simple. With your right hand, press the connector gently in towards the tank, while at the same time with your left hand, press the black locking collar also towards the tank. You are pressing them both towards the tank. Now, while holding the black locking collar down, gently reverse your force on the fuel connector and remove it from the tank. If your line is pressurized, it will burp a small quantity of gas, so please, don't be smoking or have an ignition source anywhere nearby and also don't have your face right down there unless you enjoy gas in the eye!
I have made a video of me disconnecting and reconnecting this connector. Please look at it and it will become totally clear how to do it.
Search YOU TUBE for Q7MWF9CvVfg and 9x9Gt30n5_s
5. Take a piece of string and loop together the fuel line, the electrical connector, and the main vent hose you just removed and tie them off towards the back of the motorcycle so that they are completely held out of your way.
6. Unscrew the bolt in the front center of the tank.
7. Now, remove the 2 bolts (1 on each side) at the rear of the fuel tank.
8. The tank is now able to be lifted off of the motorcycle and carefully set aside on a nice soft towel, out of the way.
That's it. Good Luck. There are photos in the Charcoal Canister Removal section showing each of these steps should you need photos.
You will need a new simple hose clamp for the spring clamp you removed unless you have the special tool to re-seat the original clamp.