I have a 6. 5 hp overhead valve bs that is used to move a sideroll irrigation system. It has run fine so far this season till yesterday. Now it does not want to run unless choked and then only in spurts. I can get it to run until you put a load on it then it dies. I took the bowl off to see it there might be water in it but no luck there. Drained a quite a bit of gas from the tank also. It will run full throttle for maybe 1 min then die. Any ideas?