Lawn mower repair question

[Alex Franke]

I have an inexpensive walk-behind lawn mower with a B&S engine on it that I'm trying to keep alive... I'd rather buy a part or two than replace the whole thing.

I push the little red bulb to prime the carburetor, and pull-start it, and it runs for about a second then stops -- as if it's not sucking in any new gas. I can keep it puttering along if I keep pressing the primer bulb, so I don't think it's the gas or the engine. I'm guessing it's the carburetor or the gasket, but I wanted to get another opinion before I go buy a non-returnable part.

Anything else that I should investigate or try first?

Cheapskate that I am, I'm considering the gasket alone for $3, or the whole carburetor assembly for $20, or at last resort a new mower for $140 (which I'd have to buy just for the engine because the $140 mowers only side discharge).

[Tom Slick]

I'd take apart the carburetor and clean it. if it has a fuel filter, which might be in the tank, I'd take a look at it also.
The engine is not having a major breakdown, it probably has some gunk stuck in one of the carburetor's passages.

[cgallery]

Had similar problems w/ an albeit completely different (Lawn Boy) engine. Turned out to be the coil. Eventually it took longer and longer to start. When it would start it would take longer and longer to nurse to running well (it would warm up and run fine). Finally, it just wouldn't start.

[Uncle Hook]

I agree with the previous post. The fact that the engines stops running if you stop pressing the blub sugggests the engine is not getting fuel. So the advice to clean the fuelline, fuel filter, and the carborator are good. It could also be needle setting which controls the air fuel mix. While you at it replace the air filler.

You will find a good deal of small engine troublshooting material online. Here is one example:

http://www.repairfaq.org/sam/lmfaq.htm#lmlmwns

[cabinetman]

I've got an edger with a B&S engine, and it says push bulb 3X. Well, 3X does what yours does. I tried pushing it 7-8 times, and it starts and runs fine. The float bowl probably doesn't fill fast enough with a short prime.
.

[WayneJ]

Try adding a little fuel system cleaner to the gas tank. An ounce in that small tank should help. It worked on mine.
Wayne

[viking4949]

Some more thoughts....
Check your air cleaner...A clogged air cleaner will give you the symptoms you speak of. Also, try starting it with the gas cap off. Does it run longer? If it does, the vents on your gas cap are clogged and need cleaned or replaced. This causes a vacuum in the gas tank and starves the engine. Cheap easy fixes.

Brandon

[Zenaca]

I just finished fixing one for a guy i work with that had the same problem , it was the little red bulb had a hole in it and was sucking air instead of gas

$5 for a new one it has a little sheet metal ring around it pry the old one out then take the old bulb out put in the new one then push in the new metal ring .
Dont even have to take the carb off the engine.

Then just prime it a couple of times and off to the races!

At least that is how it worked for me.


Bud

[dewi1219]

I recently had a similar experience with a Bolens (Lowe's) cheapo push mower. It had a B&S engine and would do the same thing as yours at least once per year requiring the carburetor to be cleaned or rebuilt. It had a CHEAP plastic carb, which I assume yours does too if it can be replaced for $20. I even completely replaced the carb once, and the problem returned several months later. I consider myself a fairly competent small engine wrench, but it got to be too much for me. I replaced it with a used LawnBoy 2-cycle and haven't had a problem since. If yours has the plastic carb my best advice is to dump it and get something more reliable, even if it is an older model. At least the older models are serviceable.

I always thought B&S made a decent product, but I will NOT buy another new mower with a B&S engine. Just my $.02.

[Alex Franke]

Okay, I took it all apart and cleaned it out the best I could. No luck. The air filter looks good -- same problem with the air filter off. Fuel filter (little mesh screen, I think) looks good, too. I can blow air through the holes in the gas cap, too, so I don't think it's that.

I can keep it running (very roughly) by continually pressing the bulk to squirt fuel in. I couldn't detect any holes in the red bulb, either.

Needle setting for air/fuel mix? It's over my head -- not sure where to look for that... It looks like the throttle valve is working okay.

There's a gasket and a thin gasket-like piece of flexible plastic between the carb and the gas tank which appears to have some built-in valves, but I have no idea what they're supposed to be doing... beyond the carb basics I'm a little lost. So that's why I suspected the gasket... but it's a guess...

Sears sells the B&S parts, and that carb is $20. (Yes it is plastic.)

...so it's a $20 gamble on a new carb fixing the problem for a couple more years. Problem is I'm not a gambler. I try to pick up some fuel system cleaner and see how that goes first.

Any chance this might be a bigger issue like compression? ...not sure if that theory makes sense if I can keep it puttering along by pumping the bulb... but I'm a newbie at this stuff.

[ironhat]

Look at the flexible fuel line you mentioned and see if it's particularly soft. I may be collapsing sufficiently to restrict flow. Pressing the priming bulb would probably force a bit more fuel past it temporarily.

[jonmulzer]

Pick up some SeaFoam fuel system cleaner at the auto parts store. Put a splash in the tank and the rest in your car. It works wonders in cleaning out gunk. It may look like you are fogging for mosquitoes though. That stuff works wonders.

[jhart]

SeaFoam is one of the most amazing products I've ever used for cleaning out gas lines, etc. I would probably use more than a splash though. You'll get a lot of smoking at first, but it cleans it out.

[Alex Franke]

Thanks, guys. I'll pick up some seafoam -- sounds like good stuff.

Meanwhile, I've come to realize that if you take something apart and put it back together enough times, it will eventually start working again. That or third time's a charm.

Sears didn't have the carb in stock, so I took it off again today, cleaned it up, poked around in all the holes with a bit of wire, and then after a couple of failed starts, it actually stayed running again!

It doesn't run very smoothly, but at least I got the lawn mowed. I'll see if the seafoam help it run more smoothly -- or if the next time I try to start it I'm back to where I started this thread again.

[jonmulzer]

Definitely try the SeaFoam then. It is amazing stuff. I put it in my truck for the first time at about 120K miles and within 5 miles I thought my truck was blowing up there was so much smoke coming out the exhaust. After that tank of fuel was gone she was running like new. It cleaned EVERYTHING out apparently. Now I add it at every oil change and it keeps everything running great. It cleared up a starting problem that I think was an injector not closing all the way bleeding off fuel pressure while it sat overnight and took a small stumble out also. I am a firm believer in it. If you want to see what it can do, check youtube for the name. The videos are wild!