Samll engine repair... anyone?

[Bill Webber]

I was given this relatively new lawn mower. Of course, for free, one wouldn't expect it to run. It starts right up, runs rough and smokey, then dies. I'm thinking the compression release is not closing. Anyone know how these things work? Is it something replaceable? :rolleyes:

[Rob Wright]

Bill,

I would start simple and replace the plug and drain the gas from the tank and carb bowl, replace with fresh gas.. This usually fixes the problems. I would crank a few times and spray a shot of starting fluid into the air carb with the air cleaner removed, and it should fire quickly. Use the starting fluid sparingly, it can damage the engine by running lean.
_ Rob

[Al Willits]

Is it a 2 cycle or 4?

Al

[Ben Grunow]

Sounds like you know more than me but I would start with a thorough cleaning with carb/choke cleaner (warm if possible) and clean/gap the plug. Maybe remove the carb and clean with pipe cleaners etc.

Many of the parts for these new things are not repairable. Just replaceable which makes it harder to diagnose some issues. I had a small engine that had rough running problems that were not to be solved until I replace the carb for about 30 bucks and 20 min time. Look into replacement carb from cman if all else fails.

[Jim DeLaney]

1. The small Briggs engines don't have a compression release.

2. If it's smoking when it runs, it's either sucking oil - bad valve guides, usually - if the smoke is blue/gray, or it's running way too rich if the smoke is black.

Valves are a major - high dollar - repair, but the running rich - which is a much more common problem, particularly in such a neearly new engine - can be from a stuck/misadjusted choke or a carb that's messed up. These small carbs generally don't have a float, per se, but do have a needle valve and seat that can get gummed up - usually from old fuel that's congealed. The remedy is to remove and clean the carb. GumOut works well for this. You may need to install a new needle and seat - less than five bucks at any Briggs & Stratton dealer, probably more at Sears. It's an easy job.

Good luck!

[skip coyne]

Bill,

I would start simple and replace the plug and drain the gas from the tank and carb bowl, replace with fresh gas.. This usually fixes the problems. I would crank a few times and spray a shot of starting fluid into the air carb with the air cleaner removed, and it should fire quickly. Use the starting fluid sparingly, it can damage the engine by running lean.
_ Rob
thats what I would do , I've brought to freebies back to life doing just that

wanted to add , you can also take the head off and clean the carbon out and clean the valves , just a few bolts and you don't need a new gasket , unless you screw up the old one

[Al Willits]

Missed the Briggs logo.

Check the air filter first, most common problem with them, they get plugged and the motor runs rich, and you may see smoke from that.
Drain the gas out of it if it's been in there for awhile.
Add some Sea foam, maybe half a cup, to the gas tank and fill with new gas and run it for awhile, maybe start cutting the grass and maybe in 10 mins or so, refill with gas and keep going.
New plug would be nice, but I'd wait till after a tankful of the Sea foam/gas mixture has run though it, may not need it or it may just need a cleaning.

It runs so I'd suspect poor maintenance would be the most probable cause.
Past history with these things shows poor maintenance is the biggest problem, not broken parts, so I'd try the easy stuff before taking the motor apart...:D

Al

[Bill Webber]

I know I should have spent more time on this, provided more info for you folks...

Anyway, good to hear there's no compression release mechanism. I took the plug out, and frankly it looks like new, no fouling whatsoever. The thing is blowing out lots of oil. The air filter is fouled and I think most of the oil is coming from there. I didn't check to see if it is coming from the exhaust. I wiped a lot of oil from around the air filter. I assumed at the time it was a product of some stuck compression release. Given there's no compression release, comments on where/why the oil coming back through the air filter?

Al, it's a 4 cycle..

Thanks...

[Kyle Kraft]

If it has a primer bulb on the side of the carb, there is a small hole in the end of the bulb. Air (and dirt) flows through the hole and again through another small hole (a vent) in the carburetor. If the vent hole in the carb is plugged, she won't run right. Remove the bulb, and check the vent orifice for pluggin.

[Al Willits]

Was this thing tilted or turned on its side?
That will/can cause oil to end up in the filter.

I'd wipe it clean, replace the filter and see what happens.

Al

[Bill Webber]

Was this thing tilted or turned on its side?
That will/can cause oil to end up in the filter.

I'd wipe it clean, replace the filter and see what happens.

Al

Yes, it has been tipped. I tipped it over to change/drain the oil. (I've been doing that with all kinds of mowers for many years without a problem like this) Anyway, I changed the oil and let it sit upright for a few minutes before trying to start it.

It will start on the first pull, limping and coughing. Runs for 30 seconds to a minute, then stops. It CANNOT be started again until several hours have passed. Don't know what that means.

I'm wondering if a plugged paper filter could be the only problem. It was owned by a single mom and her kids so it could easily have been over filled or tipped over the wrong way.

But, it is still puddling oil out the air filter port. I can't think how the plugged air filter could suck oil...

Anyway, I've been starting it every 3 -4 hours, when I walk by it, hoping it may work itself out. I only get to fool with a little on the weekends

[Joe Pelonio]

It sounds like the oil is fouling the car, the gas can't combust with oil in it.

In these small engines oil is "splashed" by a tab at the bottom of the piston so it should not be able to get back to the carb, and the only ways I can think of are:

1. The drain holes in the breather cavity (or breather cover on some engines) may be plugged, just remove the cover and try to clear it with a wire. Was the old oil real thick and gunky? Could even be overfilled crankcase would do that.

2. A cracked ring. That would also prevent it from running, too little compression.

It's relatively simple to replace in those little engines, and well worth the trouble on a late model free mower. Rings should run $10-15.

[Al Willits]

Are you running this with the plugged air filter???
If so, remove the air cleaner and try running it, don't cut grass just run it on a cement/tar driveway, also check oil level in it, usually the dipstick needs to be pushed all the way in, not to just where it hits the tube, used to see a lot of over ful motors because of that.

Tilting the mowers can cause oil to leak out on some mowers, my Toro does it, I now put the mower on two milk crates to change oil.
Al

[Bill Webber]

It sounds like the oil is fouling the car, the gas can't combust with oil in it.

In these small engines oil is "splashed" by a tab at the bottom of the piston so it should not be able to get back to the carb, and the only ways I can think of are:

1. The drain holes in the breather cavity (or breather cover on some engines) may be plugged, just remove the cover and try to clear it with a wire. Was the old oil real thick and gunky? Could even be overfilled crankcase would do that.

Are you talking about something around the air filter, air intake?

Yes the old was really thick.

I got these two mowers free. One runs fine, the other doesn't. IIRC the design of the dip sticks may be interchangeable. I wonder if they are different lengths and got mixed up? I'll need to check that.


2. A cracked ring. That would also prevent it from running, too little compression.

That would reduce compression and it wouldn't run good. There would be evidence of oil on the spark plug, though, right?

[Bill Webber]

Are you running this with the plugged air filter???
If so, remove the air cleaner and try running it...

That's certainly easy to do. I was thinking of the oil soaked foam pre-filters on some mowers when I cleaned it and put it back on. Now that I think some more about it, an oil soaked paper filter is likely quite different than an oil soaked foam pre-filter. :)

As I mentioned above, i need to make certain the dip sticks on the two freebies are the same length...:rolleyes:

[Al Willits]

Paper filter should have no oil on it.

See if you can find these motors online, maybe Briggs has a web site, then see if you can download the owners manual.
Hopefully they'll tell ya how much oil is needed in each motor.
Drain each motor and install the required amount of oil, then see which dipstick reads the closest to full on each.

Al

[Robert E Lee]

Check and make sure the choke is opening after it startes to run. Take the air cleaner off and you should be able to see.
Bob

[Kaptan J.W. Meek]

I'd almost bet the problem is in the carburator. You say it runs a minute and dies but won't start again.
1) does is run rough for a full minute, or just a few seconds?
clogged fuel line or filter, runs for a minute then basically runs out of gas..

2)After it dies, is the rope really hard to pull? or really easy to pull?
Oil in the cylinder, might make it really hard to pull, and wouldn't start.
After it heats up, valve seat leaks bad, so no compression.

HOWEVER, we may all be lookin at the wrong end of this thing.. Perhaps the coil is cracked... It runs till it gets hot, then won't run again till it cools?.. And if the coil is cracked, perhaps the smoking and rough running is a product of the cracked coil missfiring?.. Just a suggestion...

[Bill Webber]

Check and make sure the choke is opening after it startes to run. Take the air cleaner off and you should be able to see.
Bob

Good! I'll do that this weekend.

[Bill Webber]

I'd almost bet the problem is in the carburator. You say it runs a minute and dies but won't start again.
1) does is run rough for a full minute, or just a few seconds?
clogged fuel line or filter, runs for a minute then basically runs out of gas.. Smokey and halting for more than 10 seconds but less than a minute..varies Acts like a lot like closed chooke.


2)After it dies, is the rope really hard to pull? or really easy to pull?
Oil in the cylinder, might make it really hard to pull, and wouldn't start.
After it heats up, valve seat leaks bad, so no compression. Pull is the same before and after...


HOWEVER, we may all be lookin at the wrong end of this thing.. Perhaps the coil is cracked... It runs till it gets hot, then won't run again till it cools?.. And if the coil is cracked, perhaps the smoking and rough running is a product of the cracked coil missfiring?.. Just a suggestion...Could be, but I don't think so. I think I have a few more things to look at this weekend. Here's what I have to check so far:

See if the two dip sticks on the two freebie mowers may have been interchanged and it is overfilled with oil.

Try running it without an oil-clogged air filter

Check the choke position when it runs

clean out the breather vent... not sure where that is.

Can't get back to it 'til the weekend. The mower is in PA and I'm not. :)

Thanks... so far!

[Ronald Nelson]

Bill,

Go on the Briggs website. Plenty of trouble shooting info there.

Ron Nelson

[Bill Webber]

Al Willits suggested running it without the air filter. Tried that and it seemed to run pretty well. Still pretty smokey. Put in a new air filter. Let it run for 30 minutes or so. Most of the smoking cleared up.

Tried to restart it and it wouldn't go. that's OK. I don't need it to run that long anyway. :) I suspect after it's run a couple tanks of fresh gas it will be as good as new. I've blown out some nasty air filters over the years, never had one so plugged up the machine wouldn't run.

Now I'm wondering how the thing got oil soaked. Maybe someone turned it over the wrong way? Over filled the oil? Doesn't matter I guess. Thanks Al and the rest of you for offering suggestions.

Regards... :D

[Steven Wilson]

drain the gas that's in there and run some fresh gas (non-oxygenated if you can find it) with some seafoam mixed in, that will clear it out and it should be ready for service.

[Bill Webber]

drain the gas that's in there and run some fresh gas (non-oxygenated if you can find it) with some seafoam mixed in, that will clear it out and it should be ready for service.

Sounds like a plan! I'll give it a try. Thanks...

[Mike Henderson]

This is somewhat low probability but let me describe it anyway.

The lubrication on oil splash engines is not as good as on an oil pump system and the cylinder/rings can wear with high use. When this happens, you get a lot of blowby (combustion gas) going into the crankcase. There's a breather on the crankcase to allow this blowby to vent. When there's too much blowby, it usually blows oil out the vent which can foul the air filter if they're both on the same side of the motor.

Larger engines usually route this blowby back into the intake system (positive crankcase ventilation) but small motors used to just vent it - but my experience with small motors is somewhat old. If newer small motors route the blowby back into the intake system, this could explain what you're seeing.

I've only seen this problem on older motors with very high usage, however.

But if that's what you're seeing, the motor is usually not worth repairing.

Mike

[Brian Elfert]

My Honda mower requires that you tilt it on the side to drain the oil. There is no drain.

Anyhow, I had tilted it over the wrong way when changing blades last year. It ran like crap after the blade change. I found the filter was full of oil. I cleaned out the filter housing and replaced the paper filter to no avail.

My neighbor recommended changing the oil and sure enough it worked fne after changing the oil.

Brian Elfert