I originally thought it was a issue with heat because it shut down (ran out of gas) after getting warm-usually ran 1/2 hour But now it is bad enough it only runs 1 maybe 2 minutes then putters out. pulling choke gives it another breath of life but quickly just dies out. I added electric pump and that didn't help. gas cap is loose- new fuel lines and filter- the shut-off valve under tank is still original but if that was clogging it wouldn't run at all would it? use to get 1/2hour before dying out now 1 minute. No heat sensor on engine. Does tank have a internal filter? Ideas?