Starts with full choke. however requires additional throttle assist. stalls when choke closed (motor warmed)

It should run ok after warming up. After starting it, let it run for a minute or so and then try gradually opening the choke. You might try increasing the throttle setting at the same time. After the motor is hot, if you have to have the throttle setting increased in order to keep it running it means the idle setting needs to be increased, usually by turning a screw to keep the fuel valve from closing so much, or that there is a problem with the fuel flow......like a clogged jet or fuel passage in the carb.

Check the choke. Typically these are automatic types on most new mowers. The choke is closed during cold starts then automatically open as the engine warms (think of it like a car that fast-idles in the winter, then slows down as it warms...it's not exactly the same thing, but in theory works on the same principle).
What could be happening with your problem is that the choke is stuck closed or partially closed, and remains closed after the engine warms. When the choke is closed when the engine is warm, it floods the engine with fuel and stalls (and can be difficult to restart, if you can get it to restart).


To test if this is your issue, operate it until it's warm and quits. Remove the air filter and check that the butterfly valve at the top of the carburetor is open. If it's closed, open it all the way (might have to put a screwdriver, or something in there to hold it open), then try to restart it. If it's open all the way, there is likely a fuel flow restriction to the carb, or in the carb, but these problems typically cause problems running the engine hot or cold.

Two recommendations.
1. Remove carburetor, and clean with spray carb cleaner. The choke is the butterfly valve visible where the air filter attaches. Check the linkage for debris, bent or restricted linkage. After cleaning and re installation, check for free movement of butterfly choke valve.
2. Prevention. There is not a lot that can be done, but to clean the carb/choke and throttle linkage during spring tune up before first use. May require more cleaning depending on amount of use. ALWAYS USE 100% GAS, NO ETHANOL. If you must use ethanol because 100% gas in unavailable, always mix with an additive that neutralizes the effect of the ethanol. Infrequently used engines (unlike cars) that use ethanol are prone to problems because the fuel system retains water. Carburetors do not like water, cause corrosion, and repairs can be costly. For example, Someone just gave me a nice (fairly new) Bolens Riding Mower (38" B&S engine - worth about $800 ) that would not run, they just got tired of it not running right and the cost of repair shop work was about $200. I bought a $65 carb on Amazon and now I've got a nice new riding mower. They saved $.50/gal on gas and I saved $740 on a new mower...yeah, baby!

I think you are mixed up. The choke is usually closed to start a cold engine and opened once the motor warms up. The choke is closed to restrict the air flow and make the mixture richer in fuel. You can't open a choke that's already open. It's stalling because it's starved of fuel. Either a blockage or the fuel pump is not supplying enough gas.

when the choke is fully closed your choking the fuel out,, thats why when you give i t gas it dies , its not supposed to run with the choke on and getting fuel , use the choke only until the motor warms up to operating temp,, then open it,, and you should be fine,

ColdI engines require a richer mixture to operate smoothly...so they have an enricher (aka choke).
If you are finding you need to keep the choke on longer.....you may have a lean mixture than normal.nother
Start by inspecting the carb and intake manifolds for any leaks (loose fittings....cracked hoses) that could be drawing in air, leaning the mixture.

Another common issue with bikes that have sat over winter...is plugged idle jets.....the fuel varnishes the tiny orifices in the carb. You could try a product like Seafoam in the fuel tank....run it abit to get the treated fuel in the carbs then let it sit overnight...allowing time for the chemical to work. Since the bike runs fine warm...this may clear things up for you.

The choke actually just opens the throttle bodies a little (the bike is fuel injected). Try using putting on the 'choke', then pressing the start button, but dont touch the throttle. Does it start ok? Also, when started, if you use the 'choke' does it increase the engine speed? If it does not, then you need to set it up correctly.
Let us know how you get on.

Have you looked at your idle air control valve What is it? This is an electrically driven valve that allows additional control over the throttle at idle Where is it located? The IAC is located on or adjacent to the throttle body and consists of a small device held on by two bolts with an electrical connector.
How does it work? When the throttle is closed the throttle plate closes off any air from the intake manifold. In order to stop the engine from stalling due to lack of air the IAC opens a small valve allowing air to pass from the air ducting to the intake manifold. Often the IAC components consist of an air inlet port in the inside wall of the throttle body, immediately in front of the throttle plate, with a similar exit port behind the throttle plate. Connecting the two ports is a motor driven valve. When the valve is opened air effectively by-passes the closed throttle plate to maintain the engine at idle. The IAC also augments the throttle when additional power demands are put on the engine such as steering.


Symptoms of faulty IAC

• Poor starting: If the IAC fails to open or the inlet/exit ports are clogged shut with carbon the engine may start and then promptly stall. The engine can be kept running by pressing the accelerator. However any additional demand on the engine such as power steering or putting the car into drive (automatic) will cause the engine to stumble badly and often stall.
• Engine cut out: Even with the engine warmed when the vehicle is stationary such as at a red light the putting of the transmission into of 'drive' to pull away before the accelerator is pressed can cause the engine to stall. (Note this differs from the TPS fault which causes engine stall due to the accelerator being pressed too quickly)

How to check? Physically remove the IAC but keep the electrical connection to it. Temporarily block off the now open ports on the throttle, turn the engine on and examine the IAC valve action in response to additional loads (power steering inputs etc). The valve should open and close according to demand.

How to fix? If the motor of the IAC has failed then replace the IAC. If the valve is gummed closed by baked oil and carbon then clean it thoroughly with carburetor choke cleaner spray and a cloth. Similarly if the entry and exit ports on the throttle body to the IAC look blocked again clean them out thoroughly.

If you have the TB2BP EC Troybilt backpack and it bogs down or begins to stall out at full throttle with choke in FULL OPEN try the following:
1. Do the simple stuff first, Check spark plug, air filter and clean or replace if necessary.
2. Remove air filter cover, open choke and spray out the carb with carb cleaner.
3. Inspect carb and look for a flat surfaced screw with a small V notch on the side of it. It will be on the top side just forward of where the fuel lines connect. If you find it don't waste any more time looking for the High and Low fuel adjustment screws (there aren't any) this is the only adjustment other than the throttle adjustment screw you'll find.
4. Start your blower allow time for it to warm up and advance choke as far open as you can without stalling motor (mine just suddenly wouldn't run in anything other than full choke).
5. With motor running, adjust the screw to improve operation. Depending on your initial choke setting you may have to adjust, open choke to next position and fine tune.
6. Note- clockwise reduces fuel to carb, while counter clockwise increases it (if it's stalling when you attempt to throttle up it's starved for fuel) I'm sure there's a tool designed so that some tech can charge you 100.00 to turn the adjustment screw 1/4 turn but I found that a pair of fine needle nose pliers did just fine. Pay attention to original position of the V notch and what adjustments you make ( I tend to make 1/4 turns and fine tune from there) so you can always go back to your starting point. Note I'm not a technician so I can't say this the fix for your machine but it worked on mine.