Issues with my Lawn Boy 10641

Welcome onemonk909. That looks to have a Briggs 4-cycle.

Lawn-Boy - Walk Behind Mower, Insight Self Propelled Model 10682

Is the smoke blue or more black? Also were exactly is the gas dripping from? Around the carburetor?

Blackish smoke and gas dripping around the carb sounds like some dirt has got into the carb and making the float stick thus making the engine run real rich.

Blueish smoke could be several things from a bad piston ring, crankcase gasket leak, crankcase venting problem, or maybe even something as simple as a missing seal on the oil dipstick tube. Is there oil around the air filter?

Either of the above can make the engine have a sort of knock sound as the governor opens the throttle wide open trying to keep the engine from stalling.

(Also you may well already be aware of it but some are not. When tipping the mower over to one side or the other oil can be sucked into the cylinder and take awhile to burn off all the while spitting some out the exhaust.)

My first and foremost guess would be a stuck float.

Thanks for the response!

You are correct, it's a Briggs 4-cycle.

The smoke is actually pure white to my eyes, not black or blue. There has always been a thin stream of it coming out of the exhaust when mowing. When I first bought the mower, tons of smoke kept coming out; after reading reviews online, I found that this was an issue if the mower needed more oil. So I put a lot more oil in it and the smoke dissipated. Like I say, there was always a thin stream, but nothing as much as when I first got it.

So before each mow I've always put a tiny bit of oil in. Two weeks ago I ran the mower for the first time in 6 months or so. It ran fine. Then yesterday I got half of the yard finished before it began belching out smoke.

As you can tell, I am not an engine guy. I saw that oil was spattered out beneath the exhaust port. I figured it might have too much oil, so I drained some out. Started up the mower and it ran again, finished another quarter of the yard, then it started belching out smoke again.

Checked again. Oil spattered beneath the exhaust, and now a slight drip of gas...not sure where the carb is on the engine. However the gas was dripping from the front of the engine -- the gas cap is on the back. Is that where the carb is? I could dig out the Briggs manual that came with it, maybe that will show where the carb is located.

I let it sit for a while and then started it up again. Engine sounded off a bit and a huge volley of smoke came out of the exhaust, like a huge cloud. Luckily it was a windy day, I was downwind, and the smoke blew away!

The only place there is leaking oil is where it spat out from the exhaust. Doesn't appear to be leaking around the filter or anywhere else.

I called a service place and they told me this issue sounds like a carb issue, and it would not be something covered under warranty. They said it might be that the carb needs to be cleaned out, and I have no idea how to do that.

You say it might be a stuck float. Is that something I can fix?

Should I just put more oil in it, clean off the mower, and let 'er rip for a while? Maybe some oil's in there that needs to be burned off?

Thanks again for your help.

onemonk909 said:

Thanks for the response!

You are correct, it's a Briggs 4-cycle.

The smoke is actually pure white to my eyes, not black or blue. There has always been a thin stream of it coming out of the exhaust when mowing. When I first bought the mower, tons of smoke kept coming out; after reading reviews online, I found that this was an issue if the mower needed more oil. So I put a lot more oil in it and the smoke dissipated. Like I say, there was always a thin stream, but nothing as much as when I first got it.

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I would not recommend filling it with oil above the full mark on the dipstick. That can submerge internal parts in oil that are only supposed to be sprayed with it. Also it can lead to oil blowing out of the crankcase breather vent which then connects to the carburetor. From there it get sucked into the carb and the engine has to try and burn it. Not good. Lot of bad things can happen from over filling with oil.

onemonk909 said:

So before each mow I've always put a tiny bit of oil in.

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Again, only add oil if it shows low on the dipstick. (Your manual will show how to read the dipstick.)

onemonk909 said:

Checked again. Oil spattered beneath the exhaust, and now a slight drip of gas...not sure where the carb is on the engine. However the gas was dripping from the front of the engine -- the gas cap is on the back. Is that where the carb is? I could dig out the Briggs manual that came with it, maybe that will show where the carb is located.

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The carburetor is behind the air filter. You'll see the rubber hose (fuel line) coming from the gas tank and connecting to it. Normally with a stuck float it will drip right below the carb (behind the air filter for this model) and/or make it's way into the engine through the carb and intake manifold were there it will end up getting back into the oil. Which is also bad news as gas does not make for a good lubricant.

onemonk909 said:

I called a service place and they told me this issue sounds like a carb issue, and it would not be something covered under warranty. They said it might be that the carb needs to be cleaned out, and I have no idea how to do that.

You say it might be a stuck float. Is that something I can fix?

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Cleaning of the carb requires taking the carburetor apart in pieces, cleaning, possibly replacing some parts and reassembling. Since you've admitted to not being an engine guy your best bet would be to let the service shop take care of it. Also with the chance their might be something additional going on given all the occasional smoke if there is any warranty left you'll want to take advantage of it.

In hindsight (which is always a little closer to 20/20 ) you really should have taken it to a Briggs warranty authorized repair shop at the first sign of trouble (mosquito fogging ) when you bought it new.

Once your past the warranty your on your own unless the manufacture makes the rare decision to cut you a break. It's out of the hands of the shop or the mechanic at that point as they cannot get paid unless the manufacture gives both you and them special authorization.

Been there done that both as a customer and working as a warranty authorized electronic tech for customers. :bag:

onemonk909 said:

Thanks again for your response.

I took a look at the mower, which has been sitting since Monday, and noticed a stream of oil has puddled beneath the exhaust/muffler. So it appears that it is leaking out, even when the mower isn't running.

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Is there any leakage around the area on the side of the engine by the dip stick or is it all further up directly under the muffler? I've always had a tiny bit of seepage around the O ring where the dipstick tube fits into the crankcase on mine on the Toro. But never enough to actually create a puddle.

onemonk909 said:

Given how little the mower has ran, is it safe to assume then that I've probably just put too much oil in it? When I checked the dipstick the other day, the oil level appeared to be correct.

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With it showing the right level on the dipstick any excess that has been sucked into the combustion chamber should burn off within 5 minutes or so. If it fogs heavily for longer then that something else is going on.

I have that same engine on a pressure washer that is two years old and a Toro Super Recycler that is now about 12 years old. The one on the Toro has always since new burned a very small amount of oil at times but not enough that I've bothered to really investigate. It seemed to help it a little when I switched to straight SAE 30W rather then using 10W-30. Most of the time I cannot see any blue haze. Mostly I can smell it and it is more often then not when I have it on one of the slight inclines which can cause them burn more oil then on flat ground. It probably has the better of 200 hours use on it now.

Which brings up something I forgot to ask. Is your yard level or do you have some steep terraces or hills to mow? One way to make them all smoke some is mowing a hill especially with the spark plug on the lower side.

Thanks again for your help.

I checked the mower this afternoon and the seeped-out oil was in front, beneath the muffler.

I started it up and let it run, as you mentioned above. After about 3 minutes the smoke trailed off, so I went ahead and mowed. Seemed to be back to normal, still a small stream of smoke coming out of the muffler, that same burning sort of smell.

I live in Texas, so my yard is about as flat as you can get. But in the one uphill patch I do have, I hit a big clump of grass with a weed and a huge spout of smoke came out. After a few moments it went away and got back to normal.

I finished up the quarter of the yard I hadn't gotten to when all this started on Monday. After shutting off the mower I noticed a light but steady drip coming from under the air filter area. It smells like it might be gas, but I'm not sure. I put a container there to collect it, but it stopped dripping after a while.

So then, given all of this, what do you recommend? Take it to a shop or just keep running it? To my untrained eye, I'm thinking it got too much oil in it and messed up the internal works. I'd prefer not to have to take it to the shop, but if I have to I will.

Thanks!

I took a look at the mower, which has been sitting since Monday, and noticed a stream of oil has puddled beneath the exhaust/muffler. So it appears that it is leaking out, even when the mower isn't running.

With it showing the right level on the dipstick any excess that has been sucked into the combustion chamber should burn off within 5 minutes or so. If it fogs heavily for longer then that something else is going on.