Lawn mower trouble

[Howard]

It's a 4-stroke Lawn Boy.

Was only able to get it started and going for a few seconds at a time. Once it started, it would putter out in a few seconds. It would "start up" again if I primed it (pressed the red button) but would not start otherwise.

I "started" it a few times but gave up after a while.

Any idea what's happening and what I need to do? Seems like the oil level is OK and there's fuel in the tank.

 

[MagnusTheBrewer]

Your carburetor is out of wack. Either too lean or, I suspect too rich. Do you get a strong gas smell and when it "starts" and runs for a few seconds is there a lot of smoke? Could be a clogged fuel line.

 

[Howard]

There was a lot of smoke the first few times but I think the amount of smoke tapered off as I started it more. Although I'm not sure if it's fuel or oil causing that; I kind of tipped the lawnmower (leaned it at various angles) around because in the past it seemed to help start the mower.

I don't think I had started it up since last year. Clean oil though.

 

[MagnusTheBrewer]

Pull the fuel line off the carb and make sure it's not clogged. The most common thing I've seen is the carb adjustment needle/pin vibrating loose. Even if you left the gas in the mower since last year (bad owner ) you should still be able to start it. Check the spark plug as well.

 

[Howard]

OK, I'll take it apart on Sunday.

What specifically do I need to do/look for on the carb? A loose nut?

 

[MagnusTheBrewer]

There's usually an adjustment pin/needle that allows you to alter the fuel/air mix. Look for a screw on the carb that doesn't look like it's being used to attach something. Honestly, mowers are pretty basic and form follows function.

 

[MagnusTheBrewer]

If you can determine your model number, you can find exploded parts listings here. The adjustment screw can be located by the part description.

 

[Drako]

One really obvious thing to check is the air filter - I have seen a totally dirt clogged air filter cause this as well. Just saying :\

 

[rsutoratosu]

Are you using old fuel ? I had that issue after winter, had to dump out the old fuel and use some carb cleaner. My had a little carb bowl and you can unscrew it to empty it out. Usually takes a few min of carb spraying and new fuel and it'll start normally. Check youtube, there are always some people showing you lawn mower repair

 

[skyking]

Most small 4 stroke engines do not have adjustable jets. They have a fixed small orifice jet located on the bottom of the float chamber, and it is very easy to plug up. In the Tecumseh engines it is in the side of the brass bowl retention bolt.
Older fuel will form a varnish in tanks and cans, and get by filters to come to rest there.
this jet is a few MM below static fuel level, so enough fuel will leak by a typical clog to allow a "start then die" condition.

 

[NutBucket]

In other words, run all the fuel out of the carb/tank before storing it for the season. My dad hadn't used his chipper/shredder in probably 5 years but was smart enough to make sure there was no fuel it in before storing it.

We pulled it out to sell it and after putting in fresh gas it started on the 2nd pull. Not bad.

 

[skyking]

yup, that works best. I use sta-bil but that is really only good for a year or two at most.

 

[Howard]

Damn it. Nothing looks loose and I can't get a matching model number or serial number for my unit. Guess I'll try to take off the carb bowl and see what's inside.

Also, the throttle (?) on the carb was connected to something on the engine with two bent pieces of wire, one of which has a spring attached. They fell off when I took the carb off and I have no idea how to put that stuff back on. Pics to come.

 

[Howard]

Jet might've been clogged. Cleaned it out.

Now for pictures of the wire linkage...

 

[PottedMeat]

what kind of engine is it? if it's a briggs post the model number.

 

[Howard]

Got it to work. Then 20 minutes later the same symptoms. Guess the air line wasn't that clean? At least I was able to get a lawn done.

 

[BUTCH1]

Damn it. Nothing looks loose and I can't get a matching model number or serial number for my unit. Guess I'll try to take off the carb bowl and see what's inside.

Also, the throttle (?) on the carb was connected to something on the engine with two bent pieces of wire, one of which has a spring attached. They fell off when I took the carb off and I have no idea how to put that stuff back on. Pics to come.

That's probably the governor linkage. Maybe your float is bad, I would spray some carb cleaner in there while it's running (small spurts) and see if that helps..

 

[ch33zw1z]

I had a very similar problem, turned out the air filter was wet because I left it in the rain and we had a couple days of downpours. Pulled the filter off, started no problem. I shook the filter out good and left it out to dry for a day. all set after that.

 

[WackyDan]

If it is one of those plastic carbs, you can fight it all you want but sometimes you just need to order a new one.

 

[maluckey]

I think we may be overthinking this. The ethanol in most of the gas nowadays dries out the gaskets. These mowers usually use a diaphragm and spring for a fuel pump. Dried gasket means not enough fuel. The gasket is between 1-5 bucks. They last a couple of years at best. Take you ten minutes if you've NEVER done one, and 5 if you have.

Briggs even says that their diaphragm should not be used with more than 10 percent ethanol (which most cheap gas is at nowadays). SO we are at the practical design limit of ethanol, and our lovely leaders want to add more ethanol still.

 

[Howard]

I think we may be overthinking this. The ethanol in most of the gas nowadays dries out the gaskets. These mowers usually use a diaphragm and spring for a fuel pump. Dried gasket means not enough fuel. The gasket is between 1-5 bucks. They last a couple of years at best. Take you ten minutes if you've NEVER done one, and 5 if you have.

Briggs even says that their diaphragm should not be used with more than 10 percent ethanol (which most cheap gas is at nowadays). SO we are at the practical design limit of ethanol, and our lovely leaders want to add more ethanol still.

The which gasket now?

 

[BUTCH1]

I think we may be overthinking this. The ethanol in most of the gas nowadays dries out the gaskets. These mowers usually use a diaphragm and spring for a fuel pump. Dried gasket means not enough fuel. The gasket is between 1-5 bucks. They last a couple of years at best. Take you ten minutes if you've NEVER done one, and 5 if you have.

Briggs even says that their diaphragm should not be used with more than 10 percent ethanol (which most cheap gas is at nowadays). SO we are at the practical design limit of ethanol, and our lovely leaders want to add more ethanol still.

All gas here in FL is "up to 10%" ethanol, there are a few places where you can still buy non-ethanol fuel, older small engines especially outboards cannot run ethanol in any amount without damaging the fuel system. They had to do it, folks with older outboards were having carbs fail during use, it would suck to be 15 miles offshore when this happens..

 

[bamx2]

I don't understand why the mfg of the carburetors that use diaphagms don't use a material that is more compatible with ethanol .

BTW- There are lots of DIY small engine repair videos on Youtube will be of great help to in troubleshoot iand repairing the mower .

 

[rickon66]

I vote for fuel filter if it has one.

 

[BUTCH1]

I vote for fuel filter if it has one.

Most small engines don't..