Old 8hp Briggs and Stratton stalls regularly

[gpburdell]

Hi, I'm new to the forum here and hoping to get some tips on a problem I'm having trouble figuring out. I have an old Snapper with an 8hp Briggs model 190702-2130-01 engine. This engine has been running very reliably for nearly 40 years and still runs very smooth except for a stalling issue that just started this year. What happens is that I can start the mower, it runs for about 5 minutes and stalls abruptly. I can wait a minute and it cranks back up, runs 1-2 minutes and stalls again. It does this consistently. It doesn't run rough or smoke or anything else, just abruptly stalls.

My first thought was that the float is sticking so I took the carb off and thoroughly cleaned it out and reassembled it. I also put a new air filter on it because it was time for one. This didn't help. I then bought a needle valve kit and replaced the needle valve and seal in the float bowl and that didn't help either. I verified I have a good spark, I continue to have a spark as it stalls so it's definitely a fuel issue. I've also replaced the fuel line and fuel filter so no issues with supply into the carb.

What else could be causing it to stall out regularly like this and then start back up fine after a minute or two?

Thanks,
Brian

 

[slomo]

Flush fuel tank. Install new fuel line from tank to carb. Clean it again. Blow out with compressed air and SAFETY GLASSES.

 

[mechanic mark]

Results

www.briggsandstratton.com

B&S SMALL GAS ENGINE TROUBLESHOOTING CHART - Google Search

 

[gpburdell]

Yep, I did all that already. I also did pull the engine cover and cleaned out all the fins, just to be sure it wasn't overheating but I don't think it is. I changed the oil at the beginning of the season and verified it still has the right amount of oil and the oil looks good as well.

 

[Fish]

2 things to consider.
1. Your engine may have points/condensor, which can cause screwy symptoms. If you need to repair that, just snip the wire going to the points, and install the electronic coil. No need to pull the muffler.

2. Take off the valve cover and check the valve clearances with the engine cold. That may be your trouble.

 

[gpburdell]

I know I'm a newbie here but I tried to do all the basic stuff before posting here, was looking for some new ideas. It isn't the ignition, it isn't the valve clearances, the engine runs perfectly smooth and then stalls. Let it sit a minute and it cranks up fine. I cleaned out the fuel tank, replaced fuel lines and filter already, replaced float needle valve and seat. I appreciate any other tips that might be causing this.

 

[Fish]

Tried all of the stuff? What are the valve clearances then?

Just because you see a spark is meaningless.

You need to listen to folks that have worked on this equipment for a living.

Why would I wish you to check your valve clearances?

Why would I ask you about the ignition?

 

[Fish]

If the first 2 digits of the third set of numbers are 84 or less, then the engine had points at one time.

But I am leaning toward the valve clearances, as that also happens a lot.

When overheated, the block warps slightly, and the valve area will drift slightly toward the tappets, making the clearances too small, and the engine will start and run fine, but as the valve gets hot, it will expand, and the valve will no longer seal, as the tappet is preventing it from closing.
The engine stops, and cools down a bit, and the valve contracts from cooling, letting you start the engine again, etc.
Which is why you need to check your clearances when the engine is cold.

Briggs and Stratton Valve Clearances

outdoorpowerinfo.com

 

[upupandaway]

I know I'm a newbie here but I tried to do all the basic stuff before posting here, was looking for some new ideas. It isn't the ignition, it isn't the valve clearances, the engine runs perfectly smooth and then stalls. Let it sit a minute and it cranks up fine. I cleaned out the fuel tank, replaced fuel lines and filter already, replaced float needle valve and seat. I appreciate any other tips that might be causing this.

When does it die? After you run it for 10 min? What sound does it make? does it sound bogged down or sound the same as if u killed the engine grounding the ignition.

If it stops going put, put, put and comes to a stop, get an ignition test light and run with it on your engine. When it stops\sputters, look to see if there is still spark. Maybe your ignition is starting to go bad...
Try running it and when it stalls, spray some starter fluid into the intake. If it responds, look into your carb.
Whatever. Get down an dirty to find your problem.

Step back and think what it is doing, sounds can point you to which part is not working - air+fuel+compression+ignition= running engine. That's what I do.

 

[Fish]

When the block warps, the valve seat also cocks a bit, so it has a poorer and poorer seal, and creates even more heat, making things worse.
So a proper valve job would be in order, cutting the seats and valves, not just lapping.
But this is all just speculation, which is why we do simple tests and measurements, so we don't waste time/money.