Briggs 16 won't stay running unless choked?

[pintocrazy]

I have a Briggs and Stratton 16 horse on an older Montgomery Ward riding lawn mower. The engine won't stay running unless the carb is choked a little. If I push the choke all the way in the engine will bog down and die. It runs ok with it choked a little, but lacks power and bogs down when put under load. It won't start either unless it is choked also, regardless of how long it has been running. I may have put some 92 octane gas in accidentally, would that have an effect on the performance? It does backfire after I shut it off now since I put in the 92 octane. Any ideas? I have a snowblower on the front and don't feel like shoveling, so please give me some ideas.

Thanks,
Adam

[grumpygit]

It sounds like fuel starvation.
Have you tried changing the fuel filter?

[K-B]

Like grumpygit said, I would check the filter first, then see what shape the carburetor is in. Check/change the spark plug also. Another possibility is a valve problem.

[Bronson7]

Check fuel filter first, then next, check for a vacuum leak. It's running too lean, that's why you have to choke it a bit to run. Check the tightness of the carb. You might be sucking air between the carb and the intake.
Bronson7

[trailrider894]

i go with what bronson7 said. but i have had this happen before i changed the air filter and changed the jet's unsless you can change them on this particular engine.

[Big Swooh]

I have had several Briggs engines that have had the same issue. With some of the engines that rely on a tight vacum seal to draw gas from the tank you need to make sure there are no cracks in the fuel cap. I have had people give me mowers that would only start once you put fuel in the carb and eventually die. The problem was a cracked fuel cap. Look over your cap and give it a shot.