Throttle linkange spring connection

Have you cleaned the carb power jets and blown them and there passages out with compressed air?.

My money is on a partial blockage of the main jet or the passageway to it. You're having to force it to run through the idle jet by fully choking the incoming air. There's not enough gas coming in with the choke open to allow it to run.

I'm thiniking total carb disassembly, carb cleaner and an air compressor combined with a ton of patience will take care of the issue.

try and run it with the gas cap loose the vent might be plugged

This problem is usually caused by the diaphragm unit needing replaced underneath the carburetor. I'm guessing you have the Briggs engine with the (plastic) carb directly on top of the gas tank and no float bowl on the carb. You remove the tank and carb as one unit (being careful to note the spring/linkage hookups). Then remove the 5 screws that hold the carb to the tank. Then remove the gasket and diaphragm that is between the two. The replacement kit will cost you about $4 USD. Be careful! there is also a spring under there. Don't lose it and make a note of it's placement. A pinhole or a weak diaphragm is usually what makes these engines 'surge'. Hope this helps and best of luck to you.If you decide to do this repair yourself, be sure to clean all the little holes and indents and the carb itself with carb cleaner too, but don't spray it on the gaskets.
James

The Virago's have a tendency to clog up the carb. quickly due to sitting for a short amount of time, say a month or 2. Try and run some SEAFOAM in the carb. Remove the fuel line from the tank and force the seafoam into the carb with a turkey baster. Run the carb.s dry as best you can, force the seafoam into the carb. and let it sit for a day or so.Then try and start the bike off the seafoam, it will run and make a lot of smoke. Then hook the tank back up and see if that did the trick. Sometimes it will sometimes not, you may have to pull the carb.'s and clean them by removing the bowls and soaking them in a pan of the seafoam or something similar.

Your Briggs & Stratton has a Sprint or Classic motor on it. Every few years, the diaphragm in the carburetor must be replaced.
Briggs part #495770

1. Remove the air filter assembly. This is a good time to clean and re-oil the filter.
2. Remove the 3/8" head bolt from the front of the fuel tank.
3. Remove the 1/2" head bolt from the side of the fuel tank.
4. Gently pull the fuel tank assembly toward you and tilt it away from you. While doing this, you will need to unhook the governor wire from the throttle plate.
5. Drain the gasoline (you can use it again later)
6. Remove the 5 screws that hold the carburetor on top of the fuel tank.
7. Pull the carb straight up. Be careful not to lose the spring or strainer on the bottom of the carb.
8. Remove the diaphragm.
9. Clean the carb and tank surfaces with carb cleaner spray.
10. Open the package with the new diaphragm in it. You will find 2 pieces. One is rubber, the other is paper.
11. Place the rubber diaphragm onto the fuel tank, then the paper one. Gently reinstall the carb onto the tank.
12. Push the 5 screws back into the carb. Before you tighten any of the screws, have all 5 pushed through and wiggle the carb a little, this will allow the diaphragm to align properly. Tighten the screws.
13. Reinstall the tank/carb assembly. Make sure you hook up the governor linkage.
14. Inspect the governor spring(s). They should be connected on both ends. You should not disconnect them for this repair.
15. Reinstall the air filter, gas, prime, and GO!

Good Luck!

you will need to drain all of the old gas. remove carb to clean. remove float bowl. remove jets and clean with spray carb cleaner. use a bit of thin copper wire to probe the jets. count the number of turns to close mixture screw and jot the amount down somewhere. remove mixture screw and spring and clean the bore with carb cleaner. spray into float needle hole to flush out gunk through the top. reassemble, reset mixture screw , fill tank with new gas.

Its a spring! Under the fuel tank there is a link that goes from your carb to your govenor. Replace the spring by taking off the fuel tank, romove breahter and filter assembly, and then your carb. From there you can easily remove and replace broken spring. Take caution when removing the carb so that to dont damage the gaskets!

try holding the throttle open

Get some GUMOUT carburator cleaner GAS ADDITIVE. Put about 1/2 TEASPOON in the gas tank and about 1 tablespoon per gallon into your spare gas. The float pin is probably sticking from winter non-use. This will free it ip.

You can also remove the bowl from the carburator and spray everything to immediately dissolve the varnish. Be careful not to lose the pin spring.