Lawnmower Engine Starting Tips??
 

Today I picked up an old lawnmower (looks like the push type but has an engine) with a 3HP Briggs and Stratton Horizontal engine for free (score!) And it runs too, well, sort of. I had it running pretty good, I got it to rev really well (really high and smooth, punchy on the throttle too) but it would die when I let it idle for more than a few seconds. I knew it wasn't the idle stop because it was already idling pretty high. So I tried adjusting the mixture needle and then it wouldn't start so I tried putting it back and it still wouldn't start and now it is probably way out of adjustment.

I must have tried pulling the starter 100 times with different combinations of needle setting and choke and the only thing that could get it started was a little gas right into the carb.

Most of the times I had the engine running, it seemed like it wanted probably like 3/4 choke to keep it running well.

Anyway, now I really can't get it started at all and I'm not sure what choke and needle I need. I filled it with oil because it was pretty low.

The gas and spark plug are probably old, but as stated it was running okay (until I fiddled with it of course). I will try changing the spark plug (if it isn't seized in there) but I don't really have anywhere to put the old gas so I guess I can just put some new gas in to mix with it.

Anyway, does anyone have any tips to get this thing started easily and running like a champ? I'm afraid all pull out my arm if I pull that starter any more. I looked but I couldn't find any manual or starting procedures or needle setting or anything online.

Eventually, I want to do something cool with it like make a generator or a gokart (the mower already goes really fast as it is) or something of the sort.

Re: Lawnmower Engine Starting Tips??
 

I don't have any tips, but did you possibly flood the engine? I would let it sit overnight and try again tomorrow.

Re: Lawnmower Engine Starting Tips??
 

Carb is first place I would check for blockage.
NO need to go crazy, just spray in some carb cleaner into it following the directions on the can.
About 5 bucks for a can or less.

Next I would check the muffler, or exhaust port. I had a snowblower that just would always stall out when I went up hills, and it was basically the way the little muffler was designed, that it had too much backpressure stuck in the muffler when It was in that position.

Try taking the muffler off completely.

Re: Lawnmower Engine Starting Tips??
 

Sounds like you have a dirty carb. If you can take off the carp, just clean it up, put it back on. Wonders can be done by cleaning carbs... Using a carb cleaner will help, but if the clog is in the fuel lines in the carb (sometimes happens) it won't help too much. Just take it off and check it out.

Another thing that prolly isnt the main cause but will help: check out the air filter. If you flip a lawnmower over, it usually leaks oil out the air filter and cloggs it, depending on the design. If it is dirty, just leave it off and try to run it, make sure your not anywhere where it can suck up leaves or anything.

Hope that helps.

Re: Lawnmower Engine Starting Tips??
 

This was without the air filter.

Can WD-40 or Gunk Engine Bright be used to clean the carb or do I need a real carb cleaner?

Also, do you think I should replace the spark plug or do you think it is okay?

Re: Lawnmower Engine Starting Tips??
 

I would probably change the spark plug, chances are it is corroded if it has been sitting long.

Go all out and get can of carb cleaner, spray some WD40 in the carb first and see if that will get it running again.

Also did you check the spark plug wire/connectors for corrosion?

Re: Lawnmower Engine Starting Tips??
 

You should get real carb cleaner -- if the engine is sort of starting but sputters to death, try using some cold engine start/power start spray, the directions are on the bottle, but basically you'd spray it in the intake and it primes the air with fuel. You should be able to pick this up at any auto-supply store.

As for the spark plug, take it off and see what it looks like -- if its chipped and cracked then I'd change it. Also if its some funny color, please do tell us.

Re: Lawnmower Engine Starting Tips??
 

Sanddrag,

I agree with what others said about the carb problems. Get actual carb cleaner since it's designed to loosen up and remove any varnish or build up in the carb. If this has sat for some time then it's very possible that the carb is gummed up inside. Becareful of spraying other stuff in there as it may "eat" the gaskets. You have to have both the idle and choke adjusted properly for it to run. Even though you don't have any manuals for the mower try Googling the mower's make and model, and also the Briggs and Stratton's and see if you can find any info on them. Since you removed the air cleaner you know that lack of air isn't an issue, but if the choke is out of adjustment you may have too much air coming in and this can cause starting and idling problems by messing up the fuel/air mixture. At worst case if you can't find any info on adjusting the idle and choke then set everything in the center and work from there so you atleast have a point of reference.

Taking out and looking at the sparkplug may reveal flooding if it's wet after trying to start the mower. A good clean sparkplug will definitely help it start quicker and run better. If you can find any info on the motor then also see if it has the correct sparkplug installed and that it's gapped correctly as both can also cause problems. Since it has older gas in it putting in fresh gas and checking the fuel filter (if equipped) is also something you want to do before trying to start again.

Re: Lawnmower Engine Starting Tips??
 

If the other suggestions don't work...You could try what one of my older brothers did when he was 9.

My mom went out to find him and he had completely taken apart and cleaned each piece of my dad's lawnboy lawmower... and had the pieced lined up all across the garage floor. Somehow he managed to get it back together correctly before my dad got home, and it ended up running better than it did when they bought it. It still runs great even though it's +25 years old.

Re: Lawnmower Engine Starting Tips??
 

Sandrag,
Common Briggs problems start at the carb fuel interface. If yours is one of the carb on top of the fuel tank, check for leakage in the rubber gasket or a blocked relief valve in the fuel tank gasket. Most small engine places will sell you a carb kit for a few bucks that replaces all the usual suspects. A clean spark plug is essential and I wouldn't overlook the choke operation. If it starts fine after sitting but cuts out when warm, suspect the choke. If it runs high at idle suspect a really rich mixture caused by one of the leaks from worn parts mentioned above.

Re: Lawnmower Engine Starting Tips??
 

you might be able to find a service manual for the engine at your local (main branch) library

it would tell you how to re-set the needle valves - if not screw the one you were messing with all the way in (gently) then back it out 1 full turn and try to start it. if it wont fire crank it out another 1/4 turn and keep doing this till it starts

usually these engines will hunt (speed up and slow down) if the needle is screwed in too far, and will bog down and then quit if its screwed out too far (too much fuel)

definately check the plug - if the motor was running rich its probabally fouled out (covered with carbon and shorting itself).

Re: Lawnmower Engine Starting Tips??
 

Thanks for all the tips. I'll give them a try. It is the type of briggs with the carb above the gas tank.

If I buy a new Briggs lawnmower spark plug, will it come already gapped or will I have to do that?

Re: Lawnmower Engine Starting Tips??
 

Well by the sound of it its pretty old mower. So it probably is a compound problem. So you may want to try cleaning up more than just the carb, it probably has years of dirt accumulated in way too many areas. If that doesn't fix it, at least you'll have a cleaner and more efficient engine when your done. Also did you empty all of the oil out?

Re: Lawnmower Engine Starting Tips??
 

Most likely you will get a Champion or a competitor to Champion since Briggs doesn't make thier own spark plugs that I know of.

Some plugs do come pregapped but I would still check it. You never know if it got knocked around in shipping or what not but there's a possibility that the gap could've closed up or that it was never set correctly to begin with. You can get a good feeler gauge for under $10 and it's worth it.

If the gap is closed more than it should be the motor will still run but you won't have as much power. It will start up and run but it won't be making as much power and torque as it could, and at worst case, as soon as you start putting it under load it will stall out. It would be like trying to compete in a match with your robot while it has a half dead battery. :eek:

Of course if the gap is totally closed the engine will never start or run because there won't be any spark to ignite the compressed mixture. Same is true if it's too wide, since the spark won't be able to jump the wider gap.

Re: Lawnmower Engine Starting Tips??
 

[quote=sanddrag]

The gas and spark plug are probably old, but as stated it was running okay (until I fiddled with it of course). I will try changing the spark plug (if it isn't seized in there) but I don't really have anywhere to put the old gas so I guess I can just put some new gas in to mix with it.


as probably mentioned in other posts don't mix old gas with new gas just in case theres water in the old gas from built up moisture. make sure you buy the correct sparkplug, change the oil and air filter if any.

Like i said someone probably already posted this but i know that once you do a regular tuneup it should work fine and like others have also mentioned maybe you flooded it and should just let it sit

the spark plug will come already gapped just make sure you bring the old one to a sears store they have a seperate section for lawnmower supplies and might even have a repair shop just for mowers i know the one out by me repairs mowers and has many parts for them =) good luck

Re: Lawnmower Engine Starting Tips??
 

I took out the plug and discovered it was all black so I replaced it with a Champion EZ start plug (which didn't make it start any EZer). I also replaced most all the old gas with new gas. I still can only get it to run by putting a little gas right into the carb, and then it only runs for a few seconds until all of that gas is used up. It is like it is not taking gas from the tank.

I was going to get some carb cleaner but on the can it says in capital letters "do not spray into carb when engine is not running" and I can't get the engine to run long enough to spray anything in there while it is running.

Also, the carb makes a sucking/hissing sound if that makes any difference.

Thanks.

Re: Lawnmower Engine Starting Tips??
 

Sounds like the A/F mixtures are somewhat fubar-ed.
I think the reasoning behind why the instructions (on the carb-cleaner bottle) say not to use while not running is because the stuff is pretty flammable -- if you cranked your engine right after you sprayed a bunch there's a chance something can go bad. Additionally, the engine has to suck the stuff in, also carb-cleaner has xylene, which smells bad, and is a carcinogen. Just get a pal to crank the engine continually while you spray inside the air intake.

All carbs make a hissing noise, it's part of their design to get the air flow moving around the intake... if it's pretty loud then I'd definetaly say there's stuff in your carburetor that's probably causing your engine to choke.

Re: Lawnmower Engine Starting Tips??
 

Sanddrag,
The carb has a sump tube that runs down into the gas tank and the tube has a screen filter at the bottom. If the gas had been sitting any length of time, the screen could be gummed up. As I remember the carb kit has a new screen as well. Since there is no fuel pump, the hissing sound is the carb trying to suck gas in from the tank, or bypass air around the choke or gas evaporating when it hits the hot engine parts in the intake. Since the engine runs if you squirt gas into the carb, suspect fuel delivery. You may find a manual online if you haven't looked already. B&G may group engines by family so the entire part number will not get a hit on their site. BTW, the choke (if not manual) is designed to open shortly after start. If it does not, try holding it open with a screwdriver while you start it the second time.

Re: Lawnmower Engine Starting Tips??
 

I referenced the B&S website and my other slightly different B&S engine and I know I've got the mixture needle in the ballpark.

For the carb cleaner, what's the worst that can happen, it flashes a little bit? Also, the carb is a manual choke.

For the engine model number, I haven't even found it on the engine.

I can't tell exactly where the fuel comes into the carb. The carb is mounted directly to the top of the tank though, so I suspect it is as Al says. I guess I'll just have to pull the thing apart and figure out how it works! (unfortunately in is like in the 90's outside today making for miserable outdoor work).

One question I had was is it possible it is the gas cap not venting properly and making a lower pressure when the engine tries to pull gas in? Maybe I can try loosening the cap to give it some more ventilation.

Once again, thanks for all the help. I'll try to figure out if there are any problems with the fuel supply.

Also I was wondering about one more thing. There is a rubber hose (maybe 3/8" diameter) that runs from the engine (upper part, but not on top) to the choke area of the carb. Any idea what it is for?

Re: Lawnmower Engine Starting Tips??
 

Maybe this link will be helpful: Briggs & Stratton troublshooting

Re: Lawnmower Engine Starting Tips??
 

Already saw it but thanks anyway.

I pulled the carb and gas tank off (one of those carb bolts is real tough to get to, not sure how I'm going to put it back on) and the gasket mating the two was shot. The lawnmower shop was closed so I used some red silicone rtv instead. It said not recommended for use by gasoline, probably because the gas will eat away at it, but it should work at least for a while. I'm guessing anything will be better than the rotted and split gasket that was there.

I cleaned the carb and the fuel tube screeens well with carb cleaner. Hopefully once put back together, this thing will run. I'll keep you posted!

Re: Lawnmower Engine Starting Tips??
 

I too have a problem and mostly what has been said here has been done by me:

Problem - No fuel going from the circular fuel tank (located under the carb) going to the carb

What has been checked Thus Far:
1) Made sure the fuel line is clear and getting to the circular fuel tank through its provided fuel lines.
2) Checked and cleaned Carb and any methods that get fuel into the carb.
3) Fuel & Oil has been changed as well as spark plugs and air filters are concerned.

What HASN'T been checked:
1) Primer Button which just so happens to be built into the Carb Assy. thus if I have to replace one thing I would have to replace the entire Assy.

Fuel is going from the main tank into the circular tank just not going from the circular tank to the carb. :confused:

Re: Lawnmower Engine Starting Tips??
 

Well, the carb was cleaned and sealed back on the gas tank and reinstalled on the engine. I got it to run really good for about a minute. I took it all the way through the throttle up to WOT and it was really punchy. The only thing is that is would bog down at idle, and if I did not rev it back up, I knew it would stall. So, I ran it for about a minute then I let it stall so I could adjust the idle stop screw (screwdriver wasn't withing reach while running).

Anyway, I never could get it going again. Only a few seconds at a time by putting fuel right into the carb.

So anyway, I've given up. This week I might take it to the lawnmower shop and see what they say.

Re: Lawnmower Engine Starting Tips??
 

I had a similar problem with a VW beetle's carb.

It hadn't been run for a while, and there must have been years of gunk in the carb and intake track.

Since we couldn't get it to take up fuel with out just flooding the engine and/or killing the batter, we pinched the fuel line and had someone just spritz some engine starter in the carb till it caught, and again every time it started to bog down.

It ran very poorly at first, owing to all the gunk in the engine, but after about a minute of running on ether, she was doing pretty well. We hooked up the fuel line again and from then on she managed to carborize on her own. The more she ran, the better she did, and the easier she was to start afterwords.

My suggestion is to try starting it with some starter fluid, and keep it running like that for a bit. My guess is that after a little bit of running, it will manage to take up enough gas to keep running on it's own. Then, just let it heat up at about half throttle, and run most of the tank through. Keep doing it till she's begging to get started again.

Some more conservative minds don't seem to like the idea of using so much starting fluid. I've used it a bunch, and never had anything blow up or die prematurely.

-Andy A.

Re: Lawnmower Engine Starting Tips??
 

well as part of my ongoing tuneup continues on my 2 - 3 yrs old lawnmower continues I have done the following:


Took the carb off the mower and cleaned every hole thoroughly and re-assembled it back to the mower and badda bing the mower works as good as it did when it was first bought.

Now a new project has arised: where can I get parts for a mower that could be nearly 20 yrs old ? probably no where since I checked mostly everywhere so what I have done is match the newer mower with the older one - the engine is from the same manufacturer the parts are of different construction but can be installed and should work the same way.

I shall update you all if I am successful in rigging 2001 / 2002 mower parts with a 1987 / 1990 mower

Re: Lawnmower Engine Starting Tips??
 

Your repair is easy.

There are two possible causes.
1. The ball-check valve is stuck open. This is located at the end (inside) of the tube that extends into the carb (assuming that you have the older suction feed carb).

A little carb cleaner will do the trick or replace the tube. You can test by sucking and blowing with your mouth ( boy gas tastes nasty and is poison to boot) I still use this method to test.

2. A leaking head gasket is also very common. Easy fix is to re-torque it to 150 inch lbs. You will find the bolts near the exhaust are loose and the engine is sucking in air at low conditions. Better fix is to replace the gasket.

Since this is an older engine you may want to check the level of compression - the easy test is with your baby finger. Put it in the spark plug hole (no I am not joking) and pull over the recoil. If it blows your pinkey out it has enough compression to start the compression cycle. Note: Low compression (poor) improves the faster the engine runs.

I would be happy to assist further if needed. Just contact me. I have been teaching Small Engine repair for 33 years. I am certifird by both Briggs & Stratton and Tecumseh.

Re: Lawnmower Engine Starting Tips??
 

Ok, I have an Update and a question


Do you know how a spark plug wire is constructed? (whether it has a 2 wires for + and - or just one wire)

The reason why I am asking is because on the older mower I have the following issue:

Problem: I cannot turn the mower off when I release the brake handle the mower continues to run

Cause: The Brake is worn out ( i mean after almost 15 + yrs I would be worn out to) and the Engine Zone Cable is stretched (Attaches one end at the brake and the other end to the handle)

I have bought the newer model parts and did a pre-assembly and found that the Engine Zone Cable is to long and the brake even though can be installed the same way is made for right side mounting only where as its a left mount currently installed.

What I am attempting to do is to make / attach either a dip switch or a standard house holdlight switch spliced between the starter and the spark plug - what this will do is when i flick the switch it will cut the power going to the spark plug and turn the motor off.

So if any of you happen to know alot about cars or mowers or spark plugs in general any and all help is appreciated b/c at this current moment the mower cannot be operated safely with out a way to turn it off.

Re: Lawnmower Engine Starting Tips??
 

I still haven't gotten my mower running for longer than just a little bit. I still have to take the carb off again and take the yellow plastic fuel tubes out/apart and see if they are clogged or anything. Or maybe see if there's that valve thing Al mentioned a while back.

mtaman02, for your mower I have some answers. A spark plug wire is only one wire that goes to the plug electrode. The body of the plug is grounded through the engine block. Some mowers have a little metal "stop" tab on top of the head right next to the spark plug. (my 2hp b&s didn't have it, my 3hp one had it). You just flip it over (it is sort of hinged) so it touches the top of the plug. This shorts the iginition and the ground so no spark is produced. If your engine doesn't have a tab, you can short the top of the plug to the head with a screwdriver (the metal shaft of) to stop the engine. You probably want to hold the insulated end of the screwdriver to prevent getting a nice shock. I don't think it would hurt you (I've gotten a spark plug shock a few times) but I'm not totally sure, besides, it doesn't feel good to get shocked.

In any case, don't wire a switch in series with your sparkplug wire/cable. It is not necessary and probably not a good idea.

Also, usually you can pull the choke out all the way out and it will die in about 5 seconds or you can try putting your hand over the carb opening if there is no air cleaner on there, although that may take longer and might not work.

Last, by Engine Zone Cable I assume you mean throttle cable?

Re: Lawnmower Engine Starting Tips??
 

Ok if your engine has an air cleaner assembled to the carb you would want to make sure the screws assembling the too are tight other wise for some weird reason it will not allow a little bit to no fuel to go to the carb - I found that out the hard way but yeah make sure the carb & choke is clean take it apart and just spray the appropriate cleaner into it / WD-40 =) it worked well for me and has not upset the workings of the motor.

As for the spark plug it sounds like its too much work to mess around with I was just curious if I could just hook up like a switch to cut the spark off. Shorting this that and the third is not my kind of fun.

I could try holding my hand over the carb but i really don't like the idea of having my hand next to something that gets extremely hot let alone moving.

the engine zone control cable is how the manual describes it, there is no throttle cable on it - the throttle adjustment is seperate and is actually mounted on top of the carb and choke assy. for this particular motor however i removed it since it was broken and was unable to obtain a new one due to the mowers age so what i have done is just run the mower at a high rpm to keep it from stalling out when cutting alot of greass. the engine zone control cable is basically your engine cut off / emergency brake - in case anything god forbidden happens

On the Tecumseh Motors the Brake is assembled on to a bracket which has like a bike cable attached to that end (its spring loaded or so thats what how it apears that way when you release the handle bar it shoots the brake out) the other end is attached to a handle bar which you pull back so that you can start the motor. - I'm sure you already knew that but I figured I try and explain the main function of the engine zone cable. The throttle cable on some mowers is attached either right under the handle bar or on the carb itself so that you can increase and decrease the mowers speed. which as i said before do not currently attached.

Re: Lawnmower Engine Starting Tips??
 

Here is a hint. Don't start a lawnmower on any incline. The engine would always cut out when I was using my dad's lawnmower.

Re: Lawnmower Engine Starting Tips??
 

The spark is generated by a magneto, a coil of wire that a magnet passes by while the engine is turning. One side is connected to the spark plug and the other is attached to the engine block. You could try to put a switch in the ground side of the magneto coil. Many designs do not use a wire for this so you will need to check if yours has a small wire going to a screw on the block.

Re: Lawnmower Engine Starting Tips??
 

I shall check, thanks for the tips and as always i will keep you guys posted =)


**** UPDATE ****
Well I did find that wire going to the engine block and used a "Cheap" Switch to see if it would work and it did, the only problem was that the switch broke - darn antique garbage =) oh well I'll go buy a better constructed switch tomorrow and make sure its a permanent fix.

Re: Lawnmower Engine Starting Tips??
 

Most, if not all of the old, smaller Briggs engines used a diaphragm which acted as sort of a fuel pump, on vertical crankshaft engines it was between the carburetor and gas tank, on horizontal crank engines it was under a plate on the side of the carburetor. Briggs still uses diaphragms on some vertical crank engines which are usually on cheaper mowers. Most newer engines don't even have such a thing. If it has been sitting as long as you say, I would replace it. I would also remove the carb from the tank and spray carb cleaner in every passage I could find, the blow out with compressed air. Also, if your carb is metal, make sure the mating surface to the tank is flat, this area warps very easily.
As another note, on engines that act as yours does, I would try removing the air filter assembly and choking the engine by putting your hand over the air inlet (leave the actual choke off). If the engine dies out, try choking it some more and see if it comes back.
By the way, to see how old your engine is, look at the serial #. On a Briggs, the first 2 numbers are the last 2 numbers of the year of manufacture, the next 2 numbers are the month, the next 2 are the day, the last 2 are the production line the engine was built on. On a Tecumseh, the first number is the last number of the year, you don't get to know the decade. On a Kohler, you take the first 2 numbers of the serial # and add 70 to get the year.

Re: Lawnmower Engine Starting Tips??
 

I tried that and it made the engine start and continue to run (although not very strong/fast). So what does this mean? It will not run under full choke on the carb but if I keep my hand tight against where the air cleaner usually goes, it will run. What does this mean?

Also, I found the plate on the side of the carb, but I haven't taken the carb off again to open that and inspect it.

Re: Lawnmower Engine Starting Tips??
 

EAsy - Bad headgasket like I said earlier.

Re: Lawnmower Engine Starting Tips??
 

I don't have a torque wrench (should probably get one) but to me the bolts seemed a little loose (especially the two by the exhaust) so I tried tightening them up a bit but it didn't do anything.

I haven't been able to spend much time on this thing lately because it is only cool enough to work outside before 7 in the morning or after 8 in the evening. I still have to pull the carb off again and see if there is anything wrong (like the ball-check valve you mentioned) in the little yellow plastic fuel tubes.

Maybe one of these days the weather will be cooler and it will give me break so I can work on it. I would take it to the service center but since they are the only one around here they said they are 10 weeks out ( :ahh: ) on doing any repairs or service for anyone (I guess partly because they service chain saws for the forest service so they are probably very busy).

So, maybe one day I can tear into this thing myself. They aren't especially complicated are they? Where do you start (or what are the basic steps) and what do I need to look out for in the disassembly process? Also, what should I be looking for that might be a sign of the trouble (besides the head gasket)?

Last, I noticed that the top of the piston is very black and oily and nasty looking. Does that indicate anything?

Once again, thanks to everyone for the help!

Re: Lawnmower Engine Starting Tips??
 

One easy way to tell that. Snag a can of ether and blow a little around the cyl. head. See if it speeds up. try not to spray the muffler or the plug. And don't be a bad larry (love that word) and pull the plug wire, number 1, it's old and sparks tend to leak ot that rubber boot. Number 2 the resutl ain't gonna be too pleasant....radio shack's momentary push button switches work awfully well for that and they're cheap. If it still has a carb problem, let me know, I'm the master.... :D

pull the mixture screw out of the carb, check the little rubber gasket.


If you ask me briggs' Vacu-jet and pulsa-jet and pulsa-prime carbs are the worst designed pieces of plastic junk that I have ever seen. Did I mention I hate them? The day that briggs starts using Mikuni Roundslide carbs is the day when all is right with the world.

And should you need parts let me know my shed looks like sanford and son organized and on steroids. :o :D

Re: Lawnmower Engine Starting Tips??
 

Ooooh blackness.... you're flooding it and your rings might be gone. Or it's probably just 20 years of carbon build up. Get a putty knife and scrape it off, use sand paper too but don't damage the mating surfaces. Get a can of PB Blaster and use that while cleaning it. Smells like moth balls and diesel but worth it's weight in gold.
Look down the cylinder wall if there are deep marks, don't even bother. If there are deep marks just forget it Essentially it's the second most easiest engine to fiddle with.





Let me know and send some pics along of this bad larry. If you want to get deep into it I'll give ya a hand.....from waaayyyy ovah heah!!

Re: Lawnmower Engine Starting Tips??
 

Well final update


I have now attached a switch that i bought from autozone and lemme tell you this 20 yr old mower purrs like a kitten and turns off perfectly when i turn the switch on =) thanks for all tips guys