20HP Hydrostatic 42″ Cut Riding Mower

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Remove and clean the carburetor. The high speed jet is most likely colgged and is causing the condition. I assume the fuel filter (if equiped) has been replaced. I’m also not sure of the age of this mower, but this would be a place to start. Spark plug has been replaced? Just a thought.

How to Identify and Fix Common Gardening Problems ?

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Why Does Your Lawn Mower Only Run With Choke On? Your lawn mower only runs with choke on because of a problem with the engine fuel-air mixture system, which can be caused by the carburetor, bad fuel, or air leaks. The choke compels more fuel in the combustion chamber to help the engine to turn over when cold.
An engine that will fire and run with the choke closed but dies when the choke is opened likely has debris at least partially blocking the fuel passages in the carburetor. In this condition the closed choke provides enough extra fuel to enter the engine to overcome the lack of fuel flowing through the other passages.
A Dirty Carburetor Can Cause a Lawnmower To Start Then Die

By far, the most common issue that causes a stalled motor is a dirty carburetor. The carburetor on your engine is the thing that draws in air and mixes it with the fuel.

If the choke is left on for too long, excess fuel flows into the combustion chamber, causing it to seize up and stall. If this happens, the lawn mower will need to sit idle for several hours to allow the fuel to drain out of the chamber. Turn off the choke and try again later.
If your bike is only running with the choke on, it`s probably because it`s running too lean. This can be caused by a few different things: All internal combustion engines need three things to run: fuel, air, and spark. If any of these are missing or not working properly, the engine won`t run.
Loose, Dirty or Disconnected Spark Plug in Your Lawn Mower: Check it out, clean off debris, re-connect and tighten. Dirty Air Filter: Clean or replace. Fuel Not Reaching the Engine: Tap the side of the carburetor to help the flow of gas. If this doesn`t work, you might need a new fuel filter.
Use Carburetor Cleaner

Fortunately, you can generally do this without even taking the carburetor out of the engine. Start by purchasing some commercial lawnmower carburetor cleanerOpens a new window, which comes in a simple spray can and will make it easy to clean the inside and outside of the carb.

The spark plugs are worn or damaged

If you find that your lawnmower keeps dying, or keeps stalling while cutting grass, then inspect the spark plugs. Look for signs of damage or wear. Something as simple as a cracked porcelain insulator can mean an electrode has been damaged or burned away.

As the fuel level drops, a vacuum begins to form in the fuel tank because air can get in to fill the space the consumed fuel occupied. After about 10 or 15 minutes, the vacuum will become strong enough that fuel will stop flowing to the carburetor and the lawnmower will die.
Problems in the Fuel System

Check and clean the vent. Surging is also caused by water that got into the fuel. A mower left in a heavy rain or condensation on a hot summer day can choke the engine. Empty the gas tank, properly dispose of the old fuel and try a fresh batch of gasoline.

In carburetor. The choke, a butterfly valve, reduces the intake of air and allows a fuel-rich charge to be drawn into the cylinders when a cold engine is started. As the engine warms up, the choke is gradually opened either by hand or automatically by heat- and engine-speed-responsive…
If you live in a warm climate you may not need a choke. Also, most race vehicles will use a carb without a choke. If you do require a choke, you can choose the one that best suits your needs. If you want more control, you can choose a manual choke.
A choke valve is sometimes installed in the carburetor of internal combustion engines. Its purpose is to restrict the flow of air, thereby enriching the fuel-air mixture while starting the engine.
This causes terrible acceleration and terrible fuel mileage. Cold starts good, hot starts fair, POSSIBLE sputtering and poor performance, darker (blackish not bluish ) exhaust, increased fuel consumption (lower MPG). Your car would run rich, loose power, become thirsty and show black smoke on acceleration.
This is the same for any type of garment printing including screen printing. The Choke setting slightly reduces the outside dimensions of the Underbase so that white ink does not appear outside the prints edges of the final color pass.
Clogged or Dirty Air Filters

It is one of the most common problems that cause lawnmowers to sputter. The mowers take the air from the surrounding through air filters and mix it with fuel inside the engine. So, if the air filter is clogged or dirty, it will affect the flow of air into the carburetor.

An airlock is one of the common causes why your mower won`t start after running out of fuel. An Airlock occurs when air replaces fuel in the fuel lines. As you refill your fuel tank, you could push the air towards your mower`s carburetor, which keeps the new fuel from reaching the engine.
A cold engine won`t vaporise the fuel as well as it would in warmer conditions, so the choke helps enrich the mixture (either by adding in more fuel or cutting out airflow) to increase the amount of combustible vapour available to start the engine.
With the choke on, the fuel blasts its way in and provides the carburetor with the fuel it needs. While this is relatively safe and doesn`t harm any of the internal parts of the bike, it does lead to higher consumption of fuel.
With engine running:

Spray down and around the carburetor throat to remove deposits from the throttle plate area. Do not spray down carburetor throat with engine off. Do not spray below throttle plate.

Other things that could cause this issue are bad fuel, weak/colapsed/kinked fuel line, faulty spark plug, faulty ignition/coil, oil over full, clogged air filter, plugged/dirty carburetor, worn engine parts internal rings/valves/etc.
The most common cause of a mower that runs for thirty minutes and then dies is a faulty armature. A faulty gas cap is the second most likely cause.
Whenever the blade is engaged, it rotates on a crankshaft to cut the grass. But if there is interference in this rotation, the engine can overload and shut off or lose power. Check the crankshaft connection to see if it rotates freely. Inspect the connecting hardware for damage or rust.
The most likely culprit is a dirty or clogged air filter. Issues with your fuel pump or fuel filter can also cause your engine to idle then die with any throttle. If you have an older car, it could also be a bad carburetor.

Discover Relevant Questions and Answers for Your Specific Issue

the most relevant questions and answers related to your specific issue

Have to run on half choke,just stops if i turn it off.fuel is 25 to 1. thanks alan.
ANSWER : More than likely a small passage way in the carb is clogged. You can try some carb cleaner, but you may need to disassemble the carb and clean it out. Be advised that these passageways are sometimes as fine as a human hair, and almost impossible to clear sometimes. A new carb may be required if it is worth it to you. Sorry.

Will only start and run in choked position, when throttle applied chokes out. If started with out choke and throttle position in low speed will start and run for 10 sec then like it runs out of gas.
ANSWER : I have your solution guaranteed, I fixed mine yesturday remove H L screw plastic caps and on high 11 threads exposed and on the low side 8 threads exposed. removing the plastic caps allows u further adjusting these wear out or move soo just take them things off and you will be rolling

Wont stay running – Mtd 22" Yard Machine Push Mower
ANSWER : Under neath the carby is a single brass bolt, undo it

that one bolt is a multi jet, find four holes use a fine pin and carby cleaner ,hint one is at the top were the thread starts , one is in the inside center and two in the sides
put it back in and prim and start, hope it helps

Poulan pro chain wont stay running – Poulan Pro Chain Saw 46cc 20"
ANSWER : Keep “poulan” ha ha

Echo pb500 only runs with choke open – Echo Gas Blower 162 MPH 450 CFM Blower PB500T
ANSWER : I’m not to sure about the question. But you say it runs with the chock open. Your engine will only run with the chock open. Can you clarify?

Starts right up on choke. then run inrun position for a minute and have to go back to choke to keep it running ,then it runs fine for a couple of minutes and have to go back to choke and start all over again.
ANSWER : This happens with the cover off, so not the filter.

While running what setting does the choke lever need to be placed in
ANSWER : Depending on how your unit runs, it may need to be on half choke until the motor warms up. After the motor gets hot it should run with the choke fully off.

My mantis will not stay running unless the choke is full on
ANSWER : Sounds like the fuel pump diaphram in the carb. you need to either be familar with it or take it to thae shop to replace