If it is old and isn't running without pouring gas into it I'd say the carb is dirty and needs to be cleaned. If you don't want to do that, you'll have to serve as the carb and continue to pour gas into it to keep it running. Your choice is obvious.
took carb apart changed seal emptied gas tank an d cleaned it out sprayed cleaned everything with carb cleaner put back together still want start plug is good still starts by putting gas in carb what else could it be
"Older Landmark tiller with a 5 HP motor", this sounds as if it may have a Briggs & Stratton horizontal shaft motor where the gas tank is located under the carb. IF SO: there is a diaphragm located on the side of the carb which will go bad just sitting around for a short period of time. This little rubber diaphragm is the fuel pump, pulling fuel from the tank and pushing it into the carb. Do yourself a favor and purchase a repair manual for you brand and HP motor. There will be an entire chapter on carbs which will most likely show this set-up. A new diaphragm will cost under $2 and will make a world if difference in this motor's performance.
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