Lawn Mower Engine Repair

edhead · May 26th, 2008, 09:40 PM

Have about a 10 year old push mower with a Briggs and Stratton engine. Noticed this year it is starting a lot harder. Sometimes it will rev up and down (about 1 second cycles) for a while. Sometimes it will only run for about a minute, then stall. If you prime the fuel (via a fuel primer button) it will restart and after a few times it will run normally.

I think this is an issue with the carburetor, which from some reading could probably use a rebuild. Does this sound like a correct diagnostic? And how difficult is it to rebuild the carb. I assume if I took it some place to have it done for me, that the cost would be getting close to the price of a new mower.

Any thoughts? Suggestions?

And to further complicate this post, I have a chain saw that will not run at all. But if you spray starter fluid into it, it will start up and then stop. I am thinking this too is a carb issue. Looks like my near future contains some quality time with small parts.

Nick JD · May 26th, 2008, 09:46 PM

I'm no mechanicorologist, but I'd clean and lightly oil the air filter, and put in a new spark plug. If that doesn't fix it, look at other things.

e-merlin · May 26th, 2008, 10:25 PM

Sounds like you're on the right track. Those B&S engines usually have some kind of plastic carburetor. Could be a bad needle and seat or the idle circuit is grimy. Nick has a pretty good suggestion, though. A clean air filter and a new spark plug is a really good place to start. If that fixes the problem you've avoided the time consuming experience that is rebuilding the carb.

cantolina · May 26th, 2008, 10:38 PM

Rebuilding/cleaning small carbs is really not that hard...

Take down the Model and Type numbers on the engine, and go to your nearby Tractor Supply Co.....with those numbers, you can order the parts you need...pretty inexpensive...

Lots of good info here, too... http://www.briggsandstratton.com/mai...nual_and_more/

I do a lot of carb work....I find it very enjoyable....

I prefer working on Kehin carbs on Harleys, but small engine carbs are really simple...

Two-strokes are even simpler...many times, its something you find while you tear it down a bit (like a split fuel line)...

blacklinefish · May 26th, 2008, 11:12 PM

There is a self-regulating idle, I think it is two springs. The more power the engine pulls, the more it pulls one side, so the other kicks in. I think it is vacuum powered or something. Anyhow, one of your two springs is winning. If you think you are going to rebuild that carb you can stretch the spring that is tighter. This kind of messes things up, but you can get several mowings in this way.

--gh

Tim Armstrong · May 27th, 2008, 12:05 AM

It's been thirty years since I worked on a gas lawn mower, but I recall that our old Sears mower (with a Tecumseh engine) started having carb problems caused by the fuel line deteriorating, sending bits of rubber into the carb where they clogged the jet. I had to clean it out with a needle repeatedly until I got smart and replaced the fuel line.

Just thought that might be helpful!

Cheers, Tim

martyb1 · May 27th, 2008, 12:16 AM

I bet that it is the diaphragm in the carb.On small engines they work as a fuel pump.Chances are it has either died out and leaking around the seal or has a small crack in it.It is a very common thing.Chances are that is what is wrong with your chainsaw too.If they do have a crack,sometimes they will not pump fuel and will not run at all.I had a roto-tiller that had a small crack in it and it would only run if the tank was full.With the full tank,there was enough head pressure to help the fuel flow.Once that pressure decreased,it wouldn't run.Weird
Another very common problem with a Briggs engine,but it doesn't sound like your problem,is the flywheel gets rusty and it will not make a spark.All you have to do is pull off the re-coil mechanism,spin the flywheel with a piece of emery cloth up against it and your problem is solved.I bet I have fixed 50 engines and thats all that was wrong.Very common if you are in a real humid climate or left it out in the rain

charlie chitlin · May 27th, 2008, 12:33 AM

Probably no diaphragm on that carb...maybe, though.
I've only seen diafragms on chainsaws and Harleys from about '67-69.
Float bowl with needle and seat.
If you've ever seen the inside of a carburetor, cleaning shoild be no problem.
As said, though, the pulsing is likely due to a...holy crap...it's late and I can't think of the name...but it's the thing that compensates for load on the engine and feeds more or less throttle...like on a tractor.
Yikes...
If you look at the carb, the throttle is controlled by the cable that you move yourself, and another thing on the engine that may have a spring, or some even have a thing that is moved by the fan on top of the engine.
I know I'm going to get my brain back as soon as I hit send.
Or not.

martyb1 · May 27th, 2008, 12:49 AM

The governor is what I think he is trying to remember
Here is what I was talking about

Here is a place that has all the different carbs,etc
Briggs repair

smitty54017 · May 27th, 2008, 01:43 AM

Carb rebuilds are cheap. the kits usually run around $20, sometimes less. If it's not burning oil and has been dependable otherwise, it's probably worth fixing.

getbent · May 27th, 2008, 01:51 AM

Joe-Bob · May 27th, 2008, 02:14 AM

There's a metal bowl on the bottom of the carb. It's held on by the jet itself--looks like a brass bolt. Take off the bowl, clean the debris from it, blow compressed air through the jet's holes. Reverse removal.

younkint · May 27th, 2008, 03:11 AM

Quote:

Originally Posted by edhead

Have about a 10 year old push mower with a Briggs and Stratton engine. Noticed this year it is starting a lot harder. Sometimes it will rev up and down (about 1 second cycles) for a while. Sometimes it will only run for about a minute, then stall. If you prime the fuel (via a fuel primer button) it will restart .

When you say, "... and after a few times it will run normally," do you mean that it continues to run as it should for some time? Like 20 minutes, etc.? If it does not, you seem to be describing a vacuum leak - which I have seen many B&S prone to having. Solution: tighten the bolts holding the intake manifold to the head. I lost count a long time ago of how many times I've seen this.

If your engine eventually does run normally, then I believe you do indeed have a carb problem; possibly just dirt clogging a jet. Clean it; it's not hard. Find your fuel filter (which may be a simple screen in the tank) and clean that, also.

Good luck.

fltpkr · May 27th, 2008, 11:53 AM

What Joe Bob said, if you haven't tried that already. Next step would be a rebuild kit.

edhead · May 27th, 2008, 04:22 PM

Thanks for all the replies.

I did try the sparkplug first, but not the air cleaner, so I'll try that next. But I am leaning toward carb issues.

And Younkint, once it starts I can finish the yard, which is about an hour, so I don't think it is a vacuum leak, though I will check the intake manifold.

I never ceases to amaze me the wealth of knowledge of the members of this forum. I feel it is because the Telecaster is such a rational guitar, that the members are well rounded in all things mechanical. Ask a question on a Les Paul forum and it had better be about hair spray and spandex

Stan Martin · May 27th, 2008, 06:00 PM

and clean out the carburetor. very easy to do.

http://www.expertvillage.com/video/2...or-removal.htm

check out this link. I fixed my lawn mower in 20 minutes.

charlie chitlin · May 28th, 2008, 12:16 AM

D'oh!
Governor.
Most surging stems from this thing.

edhead · June 1st, 2008, 06:07 PM

Ended up taking the Carb off and cleaning it by spraying the heck out of it with Carb Cleaner. Also noticed that the exhaust was loose from the manifold.

After putting it back to together, it ran fine, so not sure what exactly it was, but I am happy.

I did copy the numbers off the carb down, so I may get a rebuild kit for it soon, as it couldn't hurt.

Thanks for all the suggestions.

cantolina · June 1st, 2008, 06:23 PM

Quote:

Originally Posted by edhead

Ended up taking the Carb off and cleaning it by spraying the heck out of it with Carb Cleaner. Also noticed that the exhaust was loose from the manifold.

After putting it back to together, it ran fine, so not sure what exactly it was, but I am happy.

I did copy the numbers off the carb down, so I may get a rebuild kit for it soon, as it couldn't hurt.

Thanks for all the suggestions.

If it ain't broke...don't break it....

Most likely you solved the problem....a rebuild kit ain't nothin but gaskets and a needle jet...don't worry about it...

ROADMAN · June 2nd, 2008, 02:42 AM

I just put my old 70s model McLane mower on Craigslist
it's got a 2HP Briggs & Stratton motor that won't start,
though it will fire if you spray the carb with quick start..
I'll try a couple of the tips you all suggested...and maybe I'll keep it.. it's like a relic

May 26th, 2008, 09:40 PM	#1 (permalink)
edhead Tele-Meister Join Date: Jun 2004 Location: NE Ohio Posts: 240	Lawn Mower Engine Repair Have about a 10 year old push mower with a Briggs and Stratton engine. Noticed this year it is starting a lot harder. Sometimes it will rev up and down (about 1 second cycles) for a while. Sometimes it will only run for about a minute, then stall. If you prime the fuel (via a fuel primer button) it will restart and after a few times it will run normally. I think this is an issue with the carburetor, which from some reading could probably use a rebuild. Does this sound like a correct diagnostic? And how difficult is it to rebuild the carb. I assume if I took it some place to have it done for me, that the cost would be getting close to the price of a new mower. Any thoughts? Suggestions? And to further complicate this post, I have a chain saw that will not run at all. But if you spray starter fluid into it, it will start up and then stop. I am thinking this too is a carb issue. Looks like my near future contains some quality time with small parts. __________________ "Work is the crabgrass in the lawn of life" Unemployed Floyd

May 26th, 2008, 09:46 PM	#2 (permalink)
Nick JD Friend of Leo's Join Date: May 2007 Location: North NSW, Australia Age: 36 Posts: 2,495	I'm no mechanicorologist, but I'd clean and lightly oil the air filter, and put in a new spark plug. If that doesn't fix it, look at other things. __________________

May 27th, 2008, 12:05 AM	#6 (permalink)
Tim Armstrong Moderator Poster Extraordinaire Join Date: Mar 2003 Location: Berlin, Maryland, USA Age: 49 Posts: 9,550	It's been thirty years since I worked on a gas lawn mower, but I recall that our old Sears mower (with a Tecumseh engine) started having carb problems caused by the fuel line deteriorating, sending bits of rubber into the carb where they clogged the jet. I had to clean it out with a needle repeatedly until I got smart and replaced the fuel line. Just thought that might be helpful! Cheers, Tim __________________ http://www.moodswingers.org

May 27th, 2008, 12:16 AM	#7 (permalink)
martyb1 Tele-Afflicted Join Date: Feb 2007 Location: Alberta,Canada Age: 44 Posts: 1,559 13 Photos	I bet that it is the diaphragm in the carb.On small engines they work as a fuel pump.Chances are it has either died out and leaking around the seal or has a small crack in it.It is a very common thing.Chances are that is what is wrong with your chainsaw too.If they do have a crack,sometimes they will not pump fuel and will not run at all.I had a roto-tiller that had a small crack in it and it would only run if the tank was full.With the full tank,there was enough head pressure to help the fuel flow.Once that pressure decreased,it wouldn't run.Weird Another very common problem with a Briggs engine,but it doesn't sound like your problem,is the flywheel gets rusty and it will not make a spark.All you have to do is pull off the re-coil mechanism,spin the flywheel with a piece of emery cloth up against it and your problem is solved.I bet I have fixed 50 engines and thats all that was wrong.Very common if you are in a real humid climate or left it out in the rain __________________ Before throwing it out,make sure it's not 16x13x1.75

May 27th, 2008, 12:33 AM	#8 (permalink)
charlie chitlin Friend of Leo's Join Date: Mar 2003 Location: Bucktown, Pa Age: 47 Posts: 2,288	Probably no diaphragm on that carb...maybe, though. I've only seen diafragms on chainsaws and Harleys from about '67-69. Float bowl with needle and seat. If you've ever seen the inside of a carburetor, cleaning shoild be no problem. As said, though, the pulsing is likely due to a...holy crap...it's late and I can't think of the name...but it's the thing that compensates for load on the engine and feeds more or less throttle...like on a tractor. Yikes... If you look at the carb, the throttle is controlled by the cable that you move yourself, and another thing on the engine that may have a spring, or some even have a thing that is moved by the fan on top of the engine. I know I'm going to get my brain back as soon as I hit send. Or not. __________________ Nil illigitimi carborundum http://profile.myspace.com/index.cfm...6-bf3537901a07

May 26th, 2008, 10:38 PM	#4 (permalink)
cantolina Tele-Meister Join Date: May 2008 Location: Warsaw, NY Posts: 121 5 Photos	Rebuilding/cleaning small carbs is really not that hard... Take down the Model and Type numbers on the engine, and go to your nearby Tractor Supply Co.....with those numbers, you can order the parts you need...pretty inexpensive... Lots of good info here, too... http://www.briggsandstratton.com/mai...nual_and_more/ I do a lot of carb work....I find it very enjoyable.... I prefer working on Kehin carbs on Harleys, but small engine carbs are really simple... Two-strokes are even simpler...many times, its something you find while you tear it down a bit (like a split fuel line)...

May 26th, 2008, 11:12 PM	#5 (permalink)
blacklinefish Tele-Afflicted Join Date: Jun 2006 Location: Northwest Missouri Age: 40 Posts: 1,244	There is a self-regulating idle, I think it is two springs. The more power the engine pulls, the more it pulls one side, so the other kicks in. I think it is vacuum powered or something. Anyhow, one of your two springs is winning. If you think you are going to rebuild that carb you can stretch the spring that is tighter. This kind of messes things up, but you can get several mowings in this way. --gh

May 27th, 2008, 12:49 AM	#9 (permalink)
martyb1 Tele-Afflicted Join Date: Feb 2007 Location: Alberta,Canada Age: 44 Posts: 1,559 13 Photos	The governor is what I think he is trying to remember Here is what I was talking about Here is a place that has all the different carbs,etc Briggs repair __________________ Before throwing it out,make sure it's not 16x13x1.75

May 27th, 2008, 01:43 AM	#10 (permalink)
smitty54017 Tele-Meister Join Date: Apr 2006 Location: New Richmond, WI Age: 36 Posts: 373	Carb rebuilds are cheap. the kits usually run around $20, sometimes less. If it's not burning oil and has been dependable otherwise, it's probably worth fixing. __________________ ----------------------------------------------------- Happy cows (and Packer fans) come from Wisconsin!

May 27th, 2008, 01:51 AM	#11 (permalink)
getbent Moderator Doctor of Teleocity Join Date: Mar 2006 Location: San Benito County, California Posts: 10,021 37 Photos	Carl sez...... __________________ 'never pet a burning dog'

May 27th, 2008, 02:14 AM	#12 (permalink)
Joe-Bob Friend of Leo's Join Date: Sep 2004 Location: Dallas, Texas Age: 46 Posts: 3,876	There's a metal bowl on the bottom of the carb. It's held on by the jet itself--looks like a brass bolt. Take off the bowl, clean the debris from it, blow compressed air through the jet's holes. Reverse removal. __________________ Music is the language of God.

May 27th, 2008, 11:53 AM	#14 (permalink)
fltpkr Tele-Holic Join Date: Feb 2007 Location: Oregoon Posts: 837	What Joe Bob said, if you haven't tried that already. Next step would be a rebuild kit. __________________ The preacher says all my sins is warshed away, including that Piggly Wiggly I knocked over in Yazoo.

May 27th, 2008, 04:22 PM	#15 (permalink)
edhead Tele-Meister Join Date: Jun 2004 Location: NE Ohio Posts: 240	Thanks for all the replies. I did try the sparkplug first, but not the air cleaner, so I'll try that next. But I am leaning toward carb issues. And Younkint, once it starts I can finish the yard, which is about an hour, so I don't think it is a vacuum leak, though I will check the intake manifold. I never ceases to amaze me the wealth of knowledge of the members of this forum. I feel it is because the Telecaster is such a rational guitar, that the members are well rounded in all things mechanical. Ask a question on a Les Paul forum and it had better be about hair spray and spandex __________________ "Work is the crabgrass in the lawn of life" Unemployed Floyd

May 27th, 2008, 06:00 PM	#16 (permalink)
Stan Martin Tele-Holic Join Date: Mar 2003 Location: Pepperell Posts: 806	get a can of Gumout spray and clean out the carburetor. very easy to do. http://www.expertvillage.com/video/2...or-removal.htm check out this link. I fixed my lawn mower in 20 minutes. __________________ http://www.stanmartin.net http://www.myspace.com/stanmartinsongs

May 28th, 2008, 12:16 AM	#17 (permalink)
charlie chitlin Friend of Leo's Join Date: Mar 2003 Location: Bucktown, Pa Age: 47 Posts: 2,288	D'oh! Governor. Most surging stems from this thing. __________________ Nil illigitimi carborundum http://profile.myspace.com/index.cfm...6-bf3537901a07

June 1st, 2008, 06:07 PM	#18 (permalink)
edhead Tele-Meister Join Date: Jun 2004 Location: NE Ohio Posts: 240	Ended up taking the Carb off and cleaning it by spraying the heck out of it with Carb Cleaner. Also noticed that the exhaust was loose from the manifold. After putting it back to together, it ran fine, so not sure what exactly it was, but I am happy. I did copy the numbers off the carb down, so I may get a rebuild kit for it soon, as it couldn't hurt. Thanks for all the suggestions. __________________ "Work is the crabgrass in the lawn of life" Unemployed Floyd

June 2nd, 2008, 02:42 AM	#20 (permalink)
ROADMAN Tele-Afflicted Join Date: Jan 2007 Location: delta b.c. canada Age: 53 Posts: 1,112	I just put my old 70s model McLane mower on Craigslist it's got a 2HP Briggs & Stratton motor that won't start, though it will fire if you spray the carb with quick start.. I'll try a couple of the tips you all suggested...and maybe I'll keep it.. it's like a relic