Hi, Richard always check fuel flow first to isolate the problem area otherwise the usual suspects are:
1. Fuel tank empty.
2. Fuel cap or fuel tank not venting properly.
3. Fuel filter clogged with rust or dirt.
4. Fuel valve/petcock not in the on or reserve position.
5. Vacuum line to fuel valve cracked, broken, pinched, or missing*
6. Fuel valve/petcock clogged or diaphragm cracked, cut or torn*
7. Fuel line from the fuel valve to the carburetor or fuel pump clogged, cracked, pinched, bent, broken, or missing.
8. Fuel pump not working*
9. Fuel line touching cylinder or head causing fuel to boil and vapor lock, repair by rerouting and wrapping line with convoluted tubing.
10. Carburetor inlet clogged.
11. Carburetor float or needle and seat stuck.
12. Carburetor not venting properly overflow line or bowl fitting clogged, pinched, or bent.
* If equipped or applicable.
For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have nice a day.
Gas Tank Question
How to Diagnose Motorcycle Fuel System Problems