Lawn mower oops

[Shep]

Have a low end B&S push lawn mower that I messed up. It appears that I let the oil level get to low. I had checked it last week and everything was fine. I may have had a false reading. Anyway, I was mowing on Monday and got about half-way through when the mower stopped. I thought it was the spark plug, so I changed that out. Still not starting. Then thought maybe I had flooded it trying to start it again, so I let it sit till Tuesday. Yesterday (Tuesday) still not starting. That's when I decided to check the oil. It was showing some, but extremely low on the stick. The motor is not seized up and even started once, then promptly died again on Monday, so I feel the internals are ok. I've since added oil, but it's still not starting.

Any suggestions? I'll be taking the whole thing apart this weekend if I can't get it started by then.

[dbhost]

The recipe for successful internal combustion engines is that the internals move as they should, add air and fuel at the proper ratio (carburetor) compress it all into a nice tight package, throwing a sufficiently hot spark into the mixture just prior to TDC (timing), and then letting it all leave...

Check the carb, and your timing / spark plug / wire...

If you had oil on the stick, but were just a little low, I seriously doubt internal damage. More than likely it's a crudded up carb, or if your mower is so equipped, fuel filter.

[jdon]

If all else fails, try a carb "rebuild" kit (nothing more than a gasket, rubber membrane and spring)- ~$7 through Amazon for my Sears/B&S. a 15 minute fix for hard starting, stalling, and running rough- after repeated carb cleaning, gas change and plug change had no effect. Runs like new (FWIW)- it's also a low-end B&S.

[cwsmith]

It doesn't sound like you've got any severe internal damage, as obviously nothing seized. That''s not to say that rings haven't worn to point where you've lost compresson though. You could pull the plug and check it if you or a friend has a gauge.

I'd also check the air filter. If you've let the oil go low, when was the last time you've cleaned the filter.

Gas, air, spark, and compression are the order that I'd check. Then, check the valves. Not sure of the kind of engine you have (did you mention that?), but on most engines that I've seen, they have finger valves which can get pretty gunked up over time.

I hope this helps,

CWS

[woodturner]

Have a low end B&S push lawn mower that I messed up. It appears that I let the oil level get to low.

I assume you already checked the gas level? As my mentor when I was a young engineer always reminded me "it's always the simple stuff that kills you".

I've had similar problems caused by loosening of bolts - make sure all the bolts are tight and in place. Check the cable - is the clamp loose, so the cable is not opening the throttle? Is the speed regulator wiggly thing (sorry - don't know the proper name ) free to move? There is an external pivoting part that controls the air intake that has to move freely. Hose down the linkages with carb cleaner and make sure everything is moving freely.

Check the safety interlock - another common problem area.

Those are the first things I would check.

[leehljp]

What I do in situations like this is take the plug out, put 4 or 5 drops of gas directly into the cylinder and replace the plug hand tight. Put the wire back on the plug. Then pull the rope and see if it "fires".

(An alternate is to put the gas into the cylinder and pull on the rope to "aeriate" the gas. Put the plug back in.)

IF it fires, then the problem is that it is not getting gas. IF nothing, then it may have an electrical problem.

[Shep]

What I do in situations like this is take the plug out, put 4 or 5 drops of gas directly into the cylinder and replace the plug hand tight. Put the wire back on the plug. Then pull the rope and see if it "fires".

(An alternate is to put the gas into the cylinder and pull on the rope to "aeriate" the gas. Put the plug back in.)

IF it fires, then the problem is that it is not getting gas. IF nothing, then it may have an electrical problem.

That's a great tip. I'll try this first then go from there. Everyone's replies make me feel a little better. I thought I might have to go shopping on craigslist for a replacement

[JR]

You might also think about spraying some starter fluid in the carb (available at all auto parts stores) as you yank on the cord. This will frequently give the motor enough of a boost to get things going.

JR

[Sweet Willy]

You got lucky. I had changed the oil on my John Deere and apparently did not close the drain properly. Cost me $1200 for a new engine. Like I said, you got lucky.

[Skaning]

One thing to look at. Do you have compression? If you do and mower was running ok until it stopped, did you hit something? B&S has a little feature that is verrrrry annoying but it saves cranks. There is a soft key between the crank and flywheel. Hit something (and it does not have to be large) and the key starts to shear and the motor goes out of time. May start, but will run really ratty, generally won't start though. Go there first before spending a lot on anything else. Most mower mechanics do unless the mower was just pulled out of storage and they smell stale gas.

[Shep]

One thing to look at. Do you have compression? If you do and mower was running ok until it stopped, did you hit something? B&S has a little feature that is verrrrry annoying but it saves cranks. There is a soft key between the crank and flywheel. Hit something (and it does not have to be large) and the key starts to shear and the motor goes out of time. May start, but will run really ratty, generally won't start though. Go there first before spending a lot on anything else. Most mower mechanics do unless the mower was just pulled out of storage and they smell stale gas.

I'll be taking a look at everything this weekend. Your suggestion could be the reason it's a little harder than normal to pull.

Another thought I had might be the safety handle that you have to hold down. I believe that when it is dissengaged it applies a brake to the flywheel, causing the motor to stop. I'm wondering if the brake is applies when the handle is engaged.

More to check out for sure.

[Sweet Willy]

You're right Skaning, I used to repair mowers and that IS the first thing I'd check. BTW most push mowers have the soft shear key primarily if they are direct drive, meaning the blade is bolted to the output shaft of the engine.

[unknown poster]

The handle that you hold to keep the blade running usually is connected to a solenoid in the bottom of the carb. When you let go of the handle the solenoid plugs the jet in the bottom of the carb and the motor dies. I've had motors refuse to run because of an electrical issue triggering this solenoid, it's something to check.

[LinuxRandal]

The safety cables do tend to stretch as they rust through in their sheaths. I've had two that have gone bad and been replaced. They hook at the bar up top, and seem to pull fine, but don't move down at the carburetor typically, when they do. (so your trying to start with the kill switch still on)

[JimD]

I do not maintain my mower very well either. When it gets to the point it will hardly run, or won't run, it is usually the air filter completely clogged. To finish the yard, I take it off and beat it against something until it looks like a filter again. Then maybe I get a new one. I've also run it low on oil before when I misread the dipstick after changing the oil. My solution is not to change the oil .

Jim