Won't start on gasoline

1998 Briggs & Stratton engine model 12F702 on a D&R walk-behind mini brush hog. Bought it 2nd hand in May. Ran great until a week ago. It will start with a spray of starting fluid, but won't start or run on gasoline, so we know it's getting air and spark. I took apart the fuel tank, fuel lines, carburetor. All were clean, but I cleaned them again with carb cleaner and brake cleaner. Fuel flows freely from the tank to the carb. Carb inlet is clean, jet is clean (appears to be non-removable), float operates freely and the bowl fills naturally. I bought a genuine B&S carb rebuild kit and replaced the needle valve, gaskets. This carb has no choke, idle or mixture screws, no adjustments. It seems fuel is not getting past the carb. Any suggestions, outside of a "new" carb?

Does yours have a primer or choke system?

The bowl nut I believe is the jet? Is is clean and holes open?

You said it has no choke, which means it has a primer system, right? If I’m right, have you checked to see if fuel is shooting into the air horn when you press the primer bulb? Second, when you rebuilt the carb, did you check the float height? When carb is inverted the float should be level or slightly lower away from float pin. If not fuel level in the float bowl may be to low. Andrew, if you read the original post you would see that the OP said it has NO CHOKE. If you post back please include type and code numbers for the engine.

andrewslarge said:

Does yours have a primer or choke system?

The bowl nut I believe is the jet? Is is clean and holes open?

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There is no choke. The primer bulb seems to be working. The bowl nut is also clean, holes open.

Rivets said:

You said it has no choke, which means it has a primer system, right? If I’m right, have you checked to see if fuel is shooting into the air horn when you press the primer bulb? Second, when you rebuilt the carb, did you check the float height? When carb is inverted the float should be level or slightly lower away from float pin. If not fuel level in the float bowl may be to low. Andrew, if you read the original post you would see that the OP said it has NO CHOKE. If you post back please include type and code numbers for the engine.

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Can't actually see fuel shooting into the air horn when the bulb is pressed, but if the engine started on ether, wouldn't it continue to run if the fuel was flowing properly? I will definitely check the float again, but there does not seem to be any adjustments for float level. Engine type: 1781F1, code: 98081758.

If fuel does not shoot into the air horn when the bulb is pressed, what's the remedy for that?

Thanks in advance for your help.

Sounds like the jet in the bowl nut is clogged.

Here's a parts diagram for that engine and carb.

It shows a needle valve, and idle speed kit, 94 and 98. Did you see them when you were in the carb? I'm confused, as you give 2 different engine identifiers, I was going off 12f702from the first post.

Do make sure the jet in the bowl nut is clear, as ilengine mentions.

or the fuel put in it has a problem. A friend one time grabbed the kerosene instead of gas. Spent a whole day trying to figure why he recently restored Packard would not run.

sgkent said:

or the fuel put in it has a problem. A friend one time grabbed the kerosene instead of gas. Spent a whole day trying to figure why he recently restored Packard would not run.

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Good point.

If the float level is too low, it may not prime or run properly. Seat may be swollen causing the change in float level. Solution is to replace the float needle and seat. Let me know what you find.