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Chris
Chris, Small Engine Technician
Category: Small Engine
Satisfied Customers: 6479
Experience:  20 years of servicing small engines of all kinds
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Briggs and Stratton 7 HP: I have an 7 HP Briggs and Stratton

Resolved Question:

I have an 7 HP Briggs and Stratton engine Model 171437, type 0530-01, code 88041810. I bought is used recently and understand that is it about 22 years old. It has never been mounted on a machine. I have disassembled, cleaned and put is a carburetor kit (B & S # XXXXX), replaced the air filter and fuel filter and hoses and put in fresh fuel. The inside of the fuel tank looks like new and there is fuel flow to the carb. Compression with the starter rope feels good. The spark plug appears nearly new. The engine will start and the throttle shaft goes to the "full throttle" position but the engine does not come up to full speed and puts out black smoke. The engine sounds like it is working hard under load but it is not connected to anything just bolted down. All the adjustable screws were set at 1 1/2 turns from off the seat. The carb is a two-piece horizontal Flo-Jet. I have an adjustable spark checker attached to the spark plug and it show a good spark all the time. Occasionally the engine will run normally (full speed and no smoke) for about 15 seconds but then dies. Any Ideas?
Submitted: 3 years ago.
Category: Small Engine
Expert:  Chris replied 3 years ago.

Chris :

Hello how are you

Chris :

What color is the smoke? Do you feel its burning oil or fuel

Chris :

Sorry i just noticed black smoke. After sitting that amount of time the rings become weak. Likely your oil rings are allowing leakage

Chris :

To confirm this you can preform a leakdown test. This test is a way to determine whats going on inside the engine without disassembly. Are you farmiliar with the test?

Chris :

Here is a link with the process and how it works, it also expalins how to build one yourself

Chris :

If you have further questions or problems let me know. Please remember to click on the accept button at the end of this chat, it is the only way i am compensated for my time...Thanks

Customer:

Black smoke like it is getting excess fuel not blue smoke from oil. When the engine does run normally for a few seconds there is no smoke at all. I will talk to my brother .. I think he has a cylinder leak detector.

Chris :

Thats your best bet. Also make sure your float does not have any pin holes in it

Customer:

I have checked for cylinder leakage and it is less than 10 percent. I checked the float for leakage with no holes (I put it in hot water and watched for bubbles). The flywheel key is intact. This engine has the solid state Magnetron ignition and the spark does not seem to change while running. I have the carburetor apart again and can't find any reason this engine should not be running normally. I have double checked every passage and hole for cleanliness and being open. The bowl gasket does not cover any holes or leave any openings different from the factory gasket. The tube that goes in before the high speed adjusting screw has the same arrangement of holes as the original and all of them are open. The gas tank cap vent is open. I am out of ideas and the next thing is to take it to a shop. I am not disappointed with your response but am looking for any further ideas.

Chris :

When the engine running bad can you see fuel being dumped into the engine through the intake. Is this the origional air filter system

Customer:

I have checked the cylinder leakage and it is less than 10 %. The float does not leak (I put it in hot water and there were no bubbles). The flywheel key is intact. This engine has the solid state Magnetron module and the spark does not seem to change while the engine is running. I have removed the muffler and there is no restriction ( I can see the exhaust valve) or difference in how the engine runs. I have the carburetor apart again and cannot see any reason that this engine does run normally. All the passages are open, the bowl gasket does not cover any openings that should normally be covered and none are left open. According to my books this carburetor does not have a removable venture. Is that correct? I will check the short intake manifold for restrictions tonight.


 


The vent in the gas tank cap is open. I am not disappointed with your responses but am looking for any other areas to check.

Chris :

When the engine is acting up can you see fuel being dumped into the intake?

Customer:

I have checked the cylinder leakage and it is less than 10 %. The float does not leak (I put it in hot water and there were no bubbles). The flywheel key is intact. This engine has the solid state Magnetron module and the spark does not seem to change while the engine is running. I have removed the muffler and there is no restriction ( I can see the exhaust valve) or difference in how the engine runs. I have the carburetor apart again and cannot see any reason that this engine does run normally. All the passages are open, the bowl gasket does not cover any openings that should normally be covered and none are left open. According to my books this carburetor does not have a removable venture. Is that correct? I will check the short intake manifold for restrictions tonight.


 


The vent in the gas tank cap is open. I am not disappointed with your responses but am looking for any other areas to check.

Chris :

Do you have a valve to shut off the fuel?

Chris :

Here is a link to the carb assy you may find helpul

Chris :

If you do have a fuel shut off valve, start the engine and shut the fuel off, if it clears out we know fuel is getting past the float valve

Customer:

Sorry for the multiple entries. I am still learning this system. The engine does have the original intake system. I will look past the choke plate while it is running and let you know.

Chris :

Not a problem, sometimes these chats act funny

Customer:

I do see fuel when I look in the carb with the air cleaner pipe off. Any idea?I borrowed the carb off of a neighbor's tiller and the engine runs fine. When I get this floor project done (the engine will be going on a vibratory packer), I will compare both carburetors to find the problem. I may contact you with a follow up question. Thanks.

Chris, Small Engine Technician
Category: Small Engine
Satisfied Customers: 6479
Experience: 20 years of servicing small engines of all kinds
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Chris
Chris
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