Briggs and Stratton Engine Trouble

[Researcher1]

I have a Yard Machines Lawn Mower from MTD that I got for free from a friend to cut my grass. The mower uses a Briggs and Stratton 6HP motor, the engine code is 12H802 Type 3128-B1.

Symptoms
The mower only runs when engine starting fluid or carb cleaner is sprayed directly into the intake.

Assumption
I assume that the fuel is not getting into the motor properly or at all.

Things I have Tried
-New Spark Plug and Air Filter
-Drained the old fuel and tried new 87 octane gas
- Cleaned Carb and installed basic rebuild kit
- I cleaned the jet and the emulsion tube

Other Observations
-When I press the primer bulb about 9 times I can finally see fuel coming out of the emulsion tube into the intake or the carburetor. I am thinking that the vacuum system is not working correctly and it is not allowing the fuel to be drawn into the intake but I don't know what else to check, any help is greatly appreciated.

 

[Rivets]

You are correct, it is a fuel issue. Suggestions, take the carb apart again and either soak it in carb cleaner overnight or take it to a repair shop and have them ultrasonically clean it. When you reassemble it, make sure that you use a new gasket between the air filter base and the carb. This is part of your priming circuit and if not good and tight it will be very difficult to prime. This manual may also help.

http://dl.dropbox.com/u/12502267/B&S Service Manuals/01_270962SingleCylinderLHead.pdf

 

[Ifixdit]

I have a Yard Machines Lawn Mower from MTD that I got for free from a friend to cut my grass. The mower uses a Briggs and Stratton 6HP motor, the engine code is 12H802 Type 3128-B1.

Symptoms
The mower only runs when engine starting fluid or carb cleaner is sprayed directly into the intake.

Assumption
I assume that the fuel is not getting into the motor properly or at all.

Things I have Tried
-New Spark Plug and Air Filter
-Drained the old fuel and tried new 87 octane gas
- Cleaned Carb and installed basic rebuild kit
- I cleaned the jet and the emulsion tube

Other Observations
-When I press the primer bulb about 9 times I can finally see fuel coming out of the emulsion tube into the intake or the carburetor. I am thinking that the vacuum system is not working correctly and it is not allowing the fuel to be drawn into the intake but I don't know what else to check, any help is greatly appreciated.

Check the condition of your air cleaner gasket and replace it if it is torn or otherwise in poor condition. Sometimes the air cleaner covers can slightly warp and adding a second gasket will fix the problem. Once you replace the gasket or add a second one look inside the throat of the carb when you push the primer bulb and you should see gas being delivered to the carb. Good luck!!

 

[Researcher1]

I have doubled up on that gasket already and even added some gasket maker to ensure a good seal. After I did this is when I could finally see gas getting into the carb when pressing the primer bulb about nine times.

It still seems that it is difficult for the gas to get into the carb. I feel like I have to press the primer bulb just right to get it to pump gas into the carb. Could there be a problem with the primer bulb?

 

[SanAntonioJoe]

Yes, it could definitely be the primer bulb. The ethanol problem takes its toll on all of the soft parts, including the bulb. One quick way is to notice if it immediately reinflates after you push it in. If not, you have a leak somewhere preventing full vacuum.

One other thing to check is whether the fuel line has an inline fuel filter. If so, I would remove it to ensure you are getting good flow to the carb. Also, when you disconnect the fuel line from the carb, does the fuel flow freely? If not, you could have a partially rotten or collapsed fuel line. Good luck!

 

[Researcher1]

I have replaced the fuel line already and each time I have removed the bowl on the carb it has had gas in it. I will double check the primer bulb but it seemed to inflate normally.

The original fuel line was pretty rotted though.

 

[Rivets]

Never use gasket sealer around a carb. There are too many small passageways which could become plugged. Have you checked to make sure that your primer bulb is not cracked?

 

[Researcher1]

Never use gasket sealer around a carb. There are too many small passageways which could become plugged. Have you checked to make sure that your primer bulb is not cracked?

I didn't notice any cracks but I will check again. I will also replace the intake gasket and remove and clean the carb again tonight.

 

[Researcher1]

You are correct, it is a fuel issue. Suggestions, take the carb apart again and either soak it in carb cleaner overnight or take it to a repair shop and have them ultrasonically clean it. When you reassemble it, make sure that you use a new gasket between the air filter base and the carb. This is part of your priming circuit and if not good and tight it will be very difficult to prime. This manual may also help.

http://dl.dropbox.com/u/12502267/B&S Service Manuals/01_270962SingleCylinderLHead.pdf

As I am looking at the carburetor in the PDF. I don't think that I have the idle speed screw or the idle mixture screw. I believe I have the LMS carb shown in figure 97

 

[Researcher1]

UPDATE

So I inspected the primer bulb today and it did have a small tear so I replaced it. It now primes easier and I can see the fuel flowing up better. It still wouldn't start so I decided to inspect the carb to make sure it had the idle mixture and idle speed screws. They both werent there, but the screw hole for the idle mixture screw wasn't even threaded so I dont think my carb has that feature. I assumed the idle speed screw simply controlled how open the throttle plate was so I got it rigged up to be about 80% closed and primed it and it started but soon died again. I primed and restarted it and continually pressed the primer bulb and it would remain on as long as I pressed the primer bulb.

QUESTIONS

How do I need to set up the idle speed?
What control the fuel flow once it is started?
Could the carb still be dirty?