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My 99 345 with 500 hours has always been cold blooded. On a normal start I had to play with the choke to keep it running for the first 30 sec. Now it will not stay running without the choke even after it has warmed up. It runs real good with the choke half open, it dies if you release the choke. Thinking carburetor I dumped in some Seafoam. No help.
The tractor worked great just last week.
 

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Pilot fuel jet / low speed circuit in the carb is plugged and needs to be cleaned out, you'll probably need to get inside the carb to clean it. Common problem, especially if you use ethanol gasoline.
 

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These old lawn mower engines and fuel systems cannot handle the ethanol well in today's fuel. My first try would be to put a heavy dose of Seafoam, as mentioned earlier, in the tank and try that. If that does not work it sounds like you may have to pull the carb and do a rebuild. one other thing I remember to check is make sure your carb is tight on the intake. Over the years they get lose and you may be sucking in air from the mount and the gaskets. That is an easy find. Start the mower, try to keep it running, get a can of WD-40 and spray around the carb areas where it mounts to the intake. As you spray around the intake and you have a vacuum' leak the engine speed will change. If that is the case the carb may be loose or you need a new gasket.
 

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Sounds like you may have owned this since new. Another common problem is that the fuel lines start to degrade and shed at some point. The 345 has 18 inches or so of fuel line on the carburetor side of the fuel filter that likely needs changing if you haven't replaced it.

If it were me, I'd pull the float bowl and see what you find - a good chance that you will find a bunch of debris. I'd clean the bowl out and spray exposed carb parts with carb cleaner. Before you reassemble the carb, I would place a container beneath it and crank the engine to see if fuel is flowing, If not, you have an issue getting fuel to the carb which could be a clogged filter, bad fuel line, clogged pick up, bad or failing fuel pump, debris in the tank, etc. Assuming fuel does flow, I'd put the bowl back on and try again.

If you do find debris and haven't changed the lines, I would change the lines.
 

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The condition described is not uncommon, but there are more reasons than just the carburetor which could cause the condition to exist.

Start by checking for air leaks between the carb and the intake manifold. If you find air leaks start by tightening the carb and see if they close and stop. If not then remove the carb and either replace the gaskets or coat them on both sides with a thin coat of Permatex #2. Check for cracked hoses and fuel leaks.

If no air leaks are found then remove the carburetor bowl, as mentioned above, check the float, needle valve, clean the bowl, and blow out the carburetor passages with carb cleaner. If you have a low speed jet on the carb then back it out (CCW) 1/2 turn min and no more than 1 turn max. Doing this will allow more fuel to flow into the cylinder and by the time you've done everything I've mentioned the engine should be running, but with a rough idle. Once you get to the rough idle point slowly turn the idle jet back (CW) until the idle smooth's, but no further. If the engine RPM starts to pulse back the idle jet out 1/4 turn.

If all else fails then replace the carb with one of those $30 Chinese carbs and call it a day for another 10 years. Have fun.:good2:
 
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