Push Mower Running Rich

[99Saturn]

Small engine novice looking for some help. Mower (Craftsman 6.5 briggs and stratton) was previously running well, started up on the first pull or first few pulls every time now issue. I hit a root a week ago and broke the flywheel key. Replaced that and reassembled, went to mow the fairly neglected lawn at that point.

Engine intermittently seems to be running way too rich (black smoke, really bogged down barely running but not stalling). It seems to start out of nowhere, and can run that way for a couple of minutes before returning to normal. Happens when the mower is being pushed relatively flat or up a small incline.

I have a portion of property that has a fairly significant slope for 6 or 7 feet and i noticed it did not occur when the mower was pointed down and then pulled back up the slope. It seems (but this could be my imagination/dumb luck) that pulling it backwards sometimes snaps it out of running rich after ~20 feet (but again, this could be my imagination, it is not 100%).

Wondering what to check/look for? Already tried removing the air filter and cleaning the carb (removed and disassembled).

Couple of pictures from my last saga of the mower to give an idea:
https://bobistheoilguy.com/forums/threads/craftsman-push-mower-starts-and-stalls.370950/

 

[oil pan 4]

That sounds like class symptoms of the carburetor bowl gasket not sealing or the choke activating.

 

[SHOZ]

Or needle valve not seating. Just had that happen on my JD F510. Let a nice trail of dead gas where the fuel was being dumped out the overflow....

 

[ARCOgraphite]

Dirty air filter and/or what SHOZ just posted about needles and seat or float problems

Usually if I hit a rock or root and it stops the blade hard - that's all she wrote for that motor.

Didn't watch this video, but this guy supposedly tackles the job.

Are you aware that China sourced carbs are available for well under 20 bucks online and may be cheaper than a b&s rebuild kit. No guarantees on those cheap carbs, though. Hit or miss.

 

[The_Eric]

If it's only forward and only in WET heavy grass, it's a possibility that the plug wire is getting shorted out

 

[99Saturn]

If it's only forward and only in WET heavy grass, it's a possibility that the plug wire is getting shorted out

Thanks, it doesn’t stop immediately going backwards, just seemed like it returned to normal more frequently getting pulled backwards.

 

[99Saturn]

Guess based on the feedback I will swap in a new carb I have from a different mower. I figured cleaning would do the trick and there may have been more to consider.

 

[tnt_motorsports]

need to check the air filter first, then clean the carb. Probably wouldn't hurt to check the spark plug.

Just my $0.02

 

[Lubener]

Sticking float due to a corroded float hinge pin or a needle/seat problem. It's a very easy carb. to work on.

 

[50yr Street Mech]

That 6.5 is a Flat Head. Too easy to work on. If you're concerns are with the spark plug wire, just unbolt the recoil housing around it ( 4- 3/8" or 1/2" bolts after you take off the beauty cover. That will expose everything for you. Check the spark plug wire for any cuts or bad pinches. Take some sandpaper or a wire wheel on a drill and get the rust off the magneto magnets. I'm leaning toward the carb or primer bulb gasket myself. You may also have a coil going bad, since you say it happens under load. Coil getting hot and giving off weak spark. It's a good little engine, when they're not piston rappin. Old school Briggs. You can get a carb kit off Scamazon with a new plug for like $20 bucks. ( 0.28" gap) If it does have a primer bulb, make sure you get that gasket with it. Those tend to fail a lot. Don't lose any springs and take a pic before you take it apart. Welcome to small engine repair/diagnosis ! Have fun Oh, I took mine furthur , I installed fuel cut off valves and little plastic paper element fuel filters after the gas tank. That stupid screen in the tank doesn't catch anything.....