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