I'm losing my marbles on this one. I can concoct and build all kinds of crazy stuff but I can't keep a stinkin lawn mower running.

I've got a 5 or 6 year old Husqvarna push mower with a B&S engine (metal carb, not plastic). It has always been a great runner that fires on the first pull 90% of the time. Before this issue I can only remember it taking a third pull on a couple occasions. I've got a somewhat small yard and the mower doesn't get used all that often.

I screwed up and fed it some bad gas. The mower would start and die. i drained the tank and cleaned it out. The screen in there was iffy at best so I punched it out and installed a see through in-line filter. The carb had a little bit of scunge in the bowl so I cleaned it thoroughly, including an inspection of the needle and seat as well as holding a properly sized drill bit with my fingers to clean the jet. I then changed the oil, air filter, and plug. It got a tank of fresh gas, too.

When it all went back together it fired up and ran great for about two minutes. Then, it struggled to stay alive. At full throttle it would slow down to a weak idle before picking back up and revving to about 3/4 speed and repeating the process.

It acts like it's running out of fuel but I can see that it's getting plenty. The heat choke seems to be opening properly.

Spark seems to be a non-issue since there is no missing or smoke from incomplete burn.

What am I overlooking?

You are not alone! I bought a new cheapie Troy Bilt walk behind for occasional touch-up mowing around close quarters stuff - I have a Deere X-300 that I bought back in 2013 for the main mowing. The Troy Bilt won't start in the spring no matter what I do - and I run ethanol-free fuel. Last year I took it to a small engine guy & left it with him. He got it running no problem - he said there was junk in the carb. This spring - no start. It has a Briggs one-pull start engine. It's a 20-pull no-start. Here it is 2020 & some things are worse-engineered than things from 60 years ago.

Buy some Seafoam and some premium fuel.

What do you expect Seafoam to do in this application? The system appears to be clean.

Float level or still trash in the jet?

i have a old craftsman 9hp snow blower with a similar problem, has 9hp kohler motor,.
when i got it there was a big surging problem with it. took off the bowl and cleaned everything up. ran better but still had a surge problem,. bought a new carb for $12. didn't surge but barely ran, acts like it not getting fuel. dropped it off by my brother in law who works on small engines on the side it to look at it. been there for 4 months he hasn't had time to look at it yet.

I'd temporarily bypass the inline filter you added to see if maybe it's too restrictive. I've seen this issue once before. If that doesn't work I'd opt for a new $12 Chinese ebay carburetor. They work amazingly well and seem to last longer that the originals.

What I usually find is the jet is clogged with a white looking crap,
I believe it's corrosion caused from ethanol in the gas.

Sometimes the vent in the gas cap plugs up and it starves for fuel. Take the cap off and see if it runs longer than two minutes.

Check your idle speed and the governor linkage. I have a similar husk that did the same thing.

I found that somehow the linkage got caught, possibly by a branch and tweaked. It was binding and wouldn't regulate smoothly.

What happens if you manually cover the intake to restrict the air flow into the carb?

Vacuum/intake leaks can have goofy symptoms.

Did you replace the fuel line? I had that issue this past spring line was plugged.

I've taken to not filling the tank full, just estimating how much gas I need then run it till it's dry, even if I have to tie the safety handle down to do that.

I just tuned up my brother in laws generator. Ordered a new carb from eBay for $40 and put a new plug in it. It would do the same thing as yours until I removed the inline filter. It didn't come with a filter originally but the carb came with one. With that gone it runs great.

Hmmmmm appears. This crap gas that we now get with alcohol causes corrosion and plugs orfaces. Regular use of Seafoam prevents this. Like others have said also check the fuel cap. My tractor was cutting off while cutting the grass. I replaced the fuel filter and it still did it. Left the cap off and I ran great sitting there. Put the cap on and backed it off a turn or two and it ran well cutting last week. See what happens this week.

I'm NOT a small engine guy but I'm turning into one just to keep the fleet running. The most common problems I'm finding are carburetor problems caused by debris from tank corrosion or just the affects of today's gasoline. I religiously run a mix of Seafoam, red HEET, and premium gas and even after running a carb dry and draining the tank, I still have carburetor problems. BTW, just because it "looks" fine doesn't mean it is.

After checking all the easy stuff already posted, replace the carb.

Been there, fought the same battles, won with the new carb.

I’m not crazy old (64) and own two acres in the country since 1985 and have never had to replace the carb on any small engine. That includes mowers, tractors, motorhome generators (3), weedwackers, chain saws, power washers, boat engine, go carts, quads, motor cycles, three race track generators, snow blower, rototiller, etc. take care of the fuel and it will take care of you. Today’s fuel is JUNK. It loves eating rubber and plastic fuel lines too.

Time for EFI and a turbo.

Kevin

FYI my last push mower, bought several years ago from Sears has a B&S 'never change oil' engine and the cap says it'll take E10-E15, but not E85. So far no issues with the fuel system.

i NEVER have fuel problems with a lawnmower !
the neighbor kid does a GREAT job on my lawn !

Well, I just ordered a new $17.88 carb from Amazon for my Troy Bilt with Briggs 550EX "no start" engine. We'll see what happens! Also, I switched over to ethanol-free fuel after the last trip to the small engine guy & that did not fix my yearly spring no-start problem, AND I do use Sea Foam every fall. (I hardly ever use the mower)

This thing has been nothing but a POS ever since it was new. I maybe have 6 hours on it.

Seafoam is for use during the summer season not winter prep. Stabile fuel treatment is for winter storage.

I mow with a 14 year old Craftsman. I've been through the carb once or twice. It stared running rough a few weeks ago. I was towards the bottom of the gas in my gas can so I thought it was that. New gas didn't help. The wife tried mowing last week and it died on her. I started it back up and it sounded like it was on its last legs...barely ran. I started removing plastic covers to access the carb. For some reason I tried starting it again with the air filter off. What do you know...it ran perfectly. Put the air filter back in place and it barely ran. I had a look at the plug and it needs replacing too. 14 years isn't bad for an air filter and a plug...

The plugged air filter would sure be an easy fix. I fixed mine a couple years ago with a few holes punched through it until I could buy one at store. I think that Feets guy would have checked that by now....

This and the only thing you really changed is the fuel filter. It may be staving the bowl. Also clean the carb again with some compressed air and carb cleaner. Did you change any of the air bleed screw settings?

Why would you store a lawnmower for the winter with gas in it?

Because this system works well for me and always has.

Because in Texas grass only stops growing about 60 days a year.

I have a 15 + year old style Briggs 3 1/2 hp push mower. The kind with the metal with foam air filter and metal gas tank below the carb. I never had any issues with it. Never cleaned the carb and I only change the spark plug every couple years. The newer mowers have nothing but issues. I`ll just keep my old one.

i have a probably a 20yo craftsman lt100 rider. bought it used 11 years ago so i really don't know how old it really is. 17hp 42" cut. i have never changed the plugs or the air filter. only the belts, blades, and battery. i just changed the oil last year for the first time. i don't winterize it, just park it for the winter and remove the battery. throw the battery in in spring and it's runs after a couple of turns of the motor.

If you don't have a shop ultrasonic parts cleaner then head over to Harbor Freight and get a cheapy $79 one and sink the B&S carb in it with some cleaning solution like Simple Green for five to ten minutes. Then hit it with the air blow gun but watch that you don't blow out and lose the float needle seat......DAMHIK that.

On those carbs there's an external vent passage that gets blocked and you end up with a droning engine that is starving for fuel. I think I have a photo of it as in the past year I've worked on lots of them. After you get it running grab an inductive tach and check the running speed and adjust the governor to run between 3,400 - 3,600 rpm. 3,800 if you're daring

My zero turn mower sucks down almost a gallon of gas with every mowing, and that happens every week. It always gets fresh gas every 3 weeks, when the 2 1/2 gal can is dry.

The Craftsman 42" cut tractor before the zero turn lasted 14 years with never an issue (after I fixed the anti backfire thing in the float bowl). I ended up replacing it because the brakes were shot and the deck was showing signs of issues. My grandson turned it into a yard runner. Gene

I bought my Sears craftsman 42 inch cut tractor in 1999. She’s getting old.

feets I don't know if your carb has a black plastic cap, cover or screw on the left top side of the carb (white arrows area) that will have that vent passage when removed? That's what causes symptoms as you describe when it gets even a little blocked. If it does cleaning it with some carb cleaner and air pressure and best with an ultrasonic parts cleaner should fix it............ Sure sounds like a float bowl venting issue to me as the float bowl holds about 1-2 minutes of running time fuel.......or less.

You mean like the new one I installed when I did the rest of the work?

That sounds like it might be the issue.

Thanks!

feets, does this look like the carb you have on your mower?

That is not what I have.

Well, I just had time to install the new Chinee carb & first pull it started right up, but it runs at a low-ish RPM & it surges. There is some kind of solenoid & I'ma wondering if this is the cause of the surge? You can watch the linkage moving which causes the surge. There is no throttle control with this mower - it's either full on or off. This thing is SUCH a piece of crap!

Well it shouldn't be a dirty fuel or air passage/jet in a new carburetor. Have you tried increasing the governor running speed. Pretty simple and if you have an inductive pickup tach it's even more simple to get it to run at 3,600 - 3,800 RPM. Just takes bending a tab to do. If that doesn't take care of the surging then you need to find where the fuel starvation is happening in the fuel tank to the carburetor. Some fuel tanks have a screen type filter in the bottom of the fuel tank to the external fuel line that feeds the carb so I would start there if increasing the governor speed doesn't do the trick. Here's a simple back yard way to increase the governor speed but watch your toes, feet, hands, pets and children when you tape the safety bar to be able to walk to the front of the mover to bend the governor spring tab to adjust it while running. I usually in a pinch can access the tab without removing anything and can bend it a little at a time with the engine not running. If you can have someone start and keep it running while you check the RPM with a tach it's a lot safer. It only takes a little bending of the tab to increase the max RPM.

What the poster of this video says about the tab being pushed back by shrubbery or sticks and branches is true and the most common reason that they seem to lose power and owners bring them in for a "tune-up" or service. Very easy "fix" and way to make a happy owner.............or if you want to be underhanded and an a-hole sell them a new mower...........me I adjust the RPM no charge except for maybe a spark plug and maybe an air and fuel filter.

I had issues with the plastic carb on my B&S, after farting about with it and spending a lot of time with it in the ultrasonic cleaner I got online and bought a brand new B&S carb from B&S for about $25 delivered.

Might be time to think about that.

There's not much to these B&S carbs I rebuild them all the time,the main jet is the bowl retaining screw I know u know that,sounds like the low speed circuit has a blockage it feeds the transfer slots by the throttle blade,try revving it up & stick your thumb over the carb opening possibly sucking out the blockage,worked for me several times.