My boyfriend owns a 1982 Yamaha Virago 750 and it's getting too much gas and won't start.
Mind you that the bike had sat for 15 years before he got it. Help please.
There are many MANY reasons why a motorcycle left for such a long time will not start. As mentioned above the most important ones, are:
First of all the carburetor will have old gasoline (even water and mud, depending on where it was left for these years) deposits WILL need to be completely disassembled and cleaned AND re-calibrated.
Then there will be NO juice in the battery at all. Maybe not even a battery. It will probably be extremely oxidized and beyond charge or repair.
Now lets add some more issues that could lead to it not starting.
AFTER caring for at least a new battery, the WHOLE ignition system needs to be checked. the most simple way to do it is to remove the spark plug, put it back in it's cable and touch the frame with its body. Try to ignite the motorcycle and check for sparks. If this works and you see sparks YOU ARE VERY LUCKY but still need to check the following:
Tire condition will probably be REALLY BAD as mentioned in above comments.
Brakes, need, NEED, N E E D to be checked for proper behavior. After all you don't want your first happy ride ending bad.
ALL cables need to be inspected and probably repaired, changed because such a long stand will have it's effect on insulations. You don't want thing short circuiting.
ALL hoses will also need a good check to see any holes, punctures or just cracks ready to spill everything out.
ALL plastic hoses from air intake ALSO need to be checked for cracks that would mess with the mixture, pressure etc which also might be a reason for your bike not starting at the moment.
Suspensions, both front and read need a check for leakages and/or proper operation.
You should (or at least validate condition of) change oil, filters (both air and oil), and any other liquids such as brakes fluid, coolant if existent, (i think it's an air cooled engine so might not be present)
Finally and equally important after being able to start it, take it for a SMALL ride you need to check all your seals and gaskets for any type of leakages.
Conclusion: If your bike has been properly stored in a dark, dry place with mild temp variations for all these years it might only need a carburetor cleaning and a new battery to start it, BUT STILL YOU SHOULD CHECK everything on it and definitely change your tires. If not maybe you should reconsider restoring it or just get a new one.