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Hi from Ireland,
Mowing forty shades of green and having issues with engine. Two cylinder ride on (Simplicity with B&S engine) Issue is that the engine starts to die and leaves one spark plug very scooted after running for about 4 - 5 minutes. The only way I can complete the cut of the garden is to keep turning off the engine (which I believe cuts off fuel) and then turning it back on. WHen I cut off the engine and restart before it dies the mower engine speeds up again for about 30 seconds (suitable mix of air/fuel). It forced me to overhaul engine, new oil and filter, new plugs, carb disassembled and cleaned and put back in. Issue is still occurring though. Any suggestions would be very welcome.
Cheers,
MO

Would a faulty float switch seal cause the rich mixture by overfilling carb. Anyway to check?

Engine model and type numbers?

Scrubcadet10 said:

Engine model and type numbers?

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Hi Scrubcadet,
Model 358777
Type 0280-E1
Thanks

Sounds like one of the ignition coils is not firing. That could make a plug black. A stuck/sticking needle and seat in the carb. Get an inline spark tester and check for proper running spark.

slomo

Thanks Slomo. I’ll try that and let you know.

How clean is the air filter ?

Hi all. Thanks again for your replies. I’m only getting back to you now as parts were very slow coming from US. (Covid).
One coil wasn’t firing And other had very poor spark. I replaced both.Problem still same but now on bothe cylinders. Sparks sooted up with dry black soot.
Took carb out again and cleaned with carb cleaner and checked all passages with can of air duster. All clear. Float switch works as to cut off supply. Float floats (leak checked in sink).
Air filter is clean. I’m at a loss.Anyone see anything like this before. Thanks, MO

Mohawk said:

Hi all. Thanks again for your replies. I’m only getting back to you now as parts were very slow coming from US. (Covid).
One coil wasn’t firing And other had very poor spark. I replaced both.Problem still same but now on bothe cylinders. Sparks sooted up with dry black soot.
Took carb out again and cleaned with carb cleaner and checked all passages with can of air duster. All clear. Float switch works as to cut off supply. Float floats (leak checked in sink).
Air filter is clean. I’m at a loss.Anyone see anything like this before. Thanks, MO

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Make sure your new coils have a good strong spark, a weak spark outside the eng will be blown out under compression inside the eng. Black soot or Black smoke is fuel, maybe too much, maybe just not getting burnt. Make sure all valve train is working correctly. If all valve train is working right, it's a fuel problem and most of the time (but not 100% of the time), fuel problems are a carbs fault!

I'd rig up a gas shut off valve in the fuel line. Get it running and fouling up the plugs and shut off the fuel supply. If it smooths out and runs for several seconds the problem is in fact the float valve/needle leaking through. Some of those have a rubber tipped needle, some have a rubber ring in the carb body that the needle seats on and that can sure go bad with today's gas.

Thanks guys. I checked the needle when I had it out. It’s still sealing the inlet (couldn’t blow through when sealed) and is still soft seating. Motor does keep running and runs smoother for a few seconds when I turn off engine. I take it this is because the fuel solenoid closes cutting off fuel and the mix goes right for a few seconds.
The new coils have a very strong spark. Fuel is new hasn’t been sitting. Thanks. I’m going to get a mechanic to check. Will let you know his findings if any. Cheers guys. Thanks again.

Only 2 reasons for an engine to run rich
1) float bowl fuel level too high
2) fuel jets too big ( or missing )
Does your engine have a single barrel or twin barrel carb ?
On the latter ones the idle jets are different sizes and if you mix them up, one side will run rich & the other lean