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Jon K.
Jon K., Small Engine Diagnostic Expert
Category: Small Engine
Satisfied Customers: 5818
Experience:  Gold certified Stihl tech, Service Manager for a rental/repair shop.Certified in most small engines
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hi need help b&s 190 cc ready start mower wont start, clean

This answer was rated:

hi need help b&s 190 cc ready start mower wont start, clean fuel tank lines, bowl, carb...
got compression, got spark (cant vouch for the timing), clean air filter, less than 12 months old with bout 40 hrs service

Thank you for choosing me to help you. My name is XXXXX XXXXX I will do my best to help you find the answer you need to resolve your problem.

Can I get the model type and spec off the engine please? Also from your description I am assuming that you have no primer or choke on this engine. Can you verify that?

Here are the numbers that I am looking for.

Customer: replied 4 years ago.

yep, no choke/primer, no fuel switch, kill switch, just dead man switch on the push handlebar



model 120000 quantum 725 ex, 190 cc

Thank you. Without the full model and type I can not give you part numbers, but your problem is the automatic choke. It works of heat created by the muffler which moves the choke closed when cold and open when warm. If you remove the air filter and shoot a bit of starting fluid into the carb the engine should start and run.

The fix for this is to replace the thermostat that is attached to the muffler. This seems to be an ongoing problem with these engines

Customer: replied 4 years ago.

model stamped number is XXXXX 3425 b1 11082958


have already tried manipulating the choke manually for starting, two butterfly valves with a demand flow circuit, ether will get a couple of cycles but won't sustain

The outside (closest to the air filter) is the choke. It should be closed when the engine is cold and then open as it gets warm. If it is working correctly then I would check the main jet inside the carburetor. At the very bottom of the carb is a nut, pinch off the fuel line and remove this and then clean out the side jet - see picture


Customer: replied 4 years ago.

already checked the jet when I had it apart both side holes and central orifice is patent,


kinda bummin' even if the bimetallic had failed, one could manually adjust the choke


any other ideas?

Even if the bimetallic choke had failed you should be able to start the engine with starter fluid.
If the timing is off (you would have to have hit something) then the flywheel key could be sheared and need to be replaced
If you can get the engine to start, and then it does then the timing is not the problem and with spark the problem is in your carburetor
Customer: replied 4 years ago.

carb kit and rebuild?

As long as you can get it started on starting fluid or a little gas into the spark plug hole then yes, remove the carburetor and give it a very good cleaning and rebuild. Sometimes though even this will not fix it and you may need to replace the carb. I always start with cleaning and rebuilding the carb
Customer: replied 4 years ago.

k so it goes, plug definitely getting wet, any reccs for the kit number for this mower?

According to the numbers you sent me I have nothing on that model, and I have the most up to date info on B+S engines. You may have a number wrong on it.
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