Did you drain the excess oil?

***"I accidentally overfilled with oil"***
Can you be "sure that you actually over filled" with oil? Or did you find that the oil level "was over full" when you checked it AFTER noticing the smoke? I ask because if you changed the oil, and then the machine sat a day or so before you used it again.........the "over full" level may be due to gasoline leaking into the crankcase lube oil. There are some other indications (if true and in proper sequence) that a leaking carb float needle valve may be causing this.
***"First, the engine wont crank. I suspected bad battery or starter but when I remove the spark plug it cranks great."***
This might be due to cylinder being "hydro-locked" from gasoline in the cylinder. Did you notice any gasoline being "blown out of" the spark plug hole when cranking engine with plug out?
***" After removing and replacing the spark plug the engine cranks, starts right up, runs well for about a minute, then quits. I have also observed oil in the air cleaner."***
This too might be from gasoline in the lube oil. First off, with the lube oil level higher due to the added volume of gasoline, the oil mass inside the engine will be in contact with more rotating engine parts than it normally would. This will result in the oil being "whipped into a mist cloud". Gasoline in the lube oil will begin to evaporate as soon as the engine parts begin to warm up. The first engine components to expose heat of operation to the lube oil are the piston and cylinder wall. These two areas are exposed to the heat of combustion, and in turn, exposed to lube oil splash and mist. When the gasoline begins to evaporate out of the oil, it creates a "positive pressure" in the crankcase that can cause the engine to stop running in two ways. One way, is that the gasoline vapors being "boiled out" of the oil, will vent out of the crankcase through the crankcase breather, and enter the intake manifold of the engine. Because the vapors are entering the intake under pressure, they will "displace" most of the fresh air from entering the intake. This can also "blow oil" back toward the air filter housing. The resulting volume of "material" going into the cylinder will be "too rich" to support combustion (all fuel?-no oxygen?- will not combust!), and so the engine stops. This is the primary cause of engine stopping due to gasoline in the oil. Second way this can stop the engine. If the engine uses a "pulse-vacuum" operated fuel pump, the positive pressure in the crankcase from the gasoline vapors can overcome the normal cycle of alternating "pressure-vacuum-pressure-vacuum" pulses that occur in the crankcase as the piston moves up and down. It is the alternating pulses inside the crankcase that provide the "power" to operate the fuel pump. Because the pump operates on a "pressure to vacuum" cycle, anything that causes the crankcase to have a "positive pressure" without the change to "negative pressure" (vacuum), will cause the fuel pump to stop pumping. This is actually a "moot point" because the "over rich" induction mass is really what "kills" the engine in most cases. It's kinda like "If the over rich mix don't shut it down, the non-working fuel pump will."
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So, think about the sequence of events here. Do you really believe (or know) that you put in too much oil?
Also, does your engine use a fuel pump or gravity fed carb?

I am positive I put in the correct amount of oil when I performed oil change at the beginning of mowing season. There was no problem at first and I was able to cut lawn two or three times. The engine was a tad tough to turn over but then I noticed smoke at startup perhaps the fourth time I cut grass. When I checked the dipstick it was high and I assumed I had not gotten complete drain when I did the oil change. Yes, I have subsequently drained and refilled the oil. The carb is gravity fed. And yes, there was plenty of gas being blown out of the spark plug hole when I cranked with the plug out.

OK, gas overflowing from carb, filling cylinder, contaminating crankcase lube oil. First thing you need to do is install an inline fuel cutoff valve into the fuel hose between the fuel filter and the fuel tank. From this point forward, always turn off the fuel by closing the cutoff valve BEFORE you stop the engine. This is so you will deplete some of the fuel in the carb bowl so it will not leak into the intake manifold. Cut the fuel off any time the engine is not running, even if you are just taking a break. You will need to change the oil again. You may continue to see some oil smoke from the muffler until that gets burned out good. You might want to replace the air filter if it is really soaked with oil and gas. It is too soon to tell if you might also have a defective head gasket. Hydrostatic lock can impose a big strain on a head gasket. Hopefully you just got the smoke with no other damage. Run it normally after repairs are complete and check the oil often. Make yourself some kind of highly visible reminder note about remembering to turn off the gas valve when you stop the engine.

Hey Mownie, what about repairing the bad needle, seat, float problem along with installing a fuel "safety switch" shutoff?

Hey Atschirner, I don't have a problem with "repairing the bad needle, seat, float problem along with installing a fuel "safety switch" shutoff?........But please clarify "safety switch" shutoff. The term "safety switch" implies something electrical to me (at first glance, anyway). But if you are simply "putting it differently" about the recommended "shutoff valve", I'll go along with that OK. If you mean something "really different", let's talk :^) The reason I personally don't always suggest someone to go "headlong" into carb teardown (as a first line "cure") is because the problem causing the needle not to seat and seal TODAY..........might not be there tomorrow. AND even if you clean, repair, and replace the needle valve assembly, there is still no guarantee that a "stray piece" of debris won't get stuck in the needle and seat soon after, and leak fuel again. I have no problem if a person wants to clean and repair the needle, seat, float, but......one must accept that that, sometimes the problem of leaky needle is due to foreign matter entering the carb in the incoming fuel stream, not a "defect" in the needle & seat per se. You can install an inline fuel shutoff valve, turn off the valve while engine is still running to deplete some or all of the fuel in the carb bowl, and remedy the problem of drowning the engine with gas while in storage. Whether a person should tear the carb apart depends on whether the engine is performing well enough with the current state of the carb (despite the leaking needle during storage). It also depends on whether the person wants to do, or is capable of, carb repair. My opinion is that if the carb leaks during storage, but the machine performs ok otherwise, install the shutoff valve and skip the carb work til some time in the future. If the carb leaks and drowns the engine AND the engine runs like a dog, install the shutoff valve, replace all fuel lines, and replace the fuel filter. On fuel pump fed systems, found to be troubled with a lot of trash or debris, I even suggest that the fuel pump might end up needing to be replaced. One thing to remember is: A needle valve that leaks will drown an engine while in storage, but the same leak WILL NOT cause a rich mix or over fuel condition in a running engine. When an engine is running, the fuel is drawn out of the bowl quickly enough that the float will drop a bit, letting more fuel into the carb. The rate at which fuel leaks past a leaky needle in storage would require several hours just to fill the bowl ONE TIME. Fuel shutoff valve.....very important! Repair leaky needle valve.......less important. My opinion.

For $11 at the local mom 'n pop hardware store I got a fuel shutoff valve, clamps, and new sparkplug. Drained the fuel-laden oil from the crankcase, added new oil. Serviced air cleaner and installed sparkplug. Started right up and ran beautifully. Oil residue burned out of the muffler after a minute or two and after that no smoke. After about five minutes at idle I cut grass for about 15 minutes, all working great.

So, so far so good, and well see if the fix sticks.

I was going to ask about carb rebuild/replacement, but that has been covered already in this discussion. As the engine has always run well, and still is, Ill leave well enough alone and enjoy this cheap and easy solution. I will shoot some carb cleaner spray down the breather for good luck once I have successfully cut my ¾ acre.

A question about using the fuel shut-off valve: when finished with the engine should I use it to shut down the engine, or simply shut off the fuel supply, allow a bit of carb fuel to burn off, and then shut off the engine VIA ignition switch?

Thanks very much for the assist here folks, and I will give an update once the rain here in Maryland stops and I mow again.

Personally, for my own use, I would behave like this: During the "cutting season" (if that is the ONLY time you operate this machine), after each mowing, but before parking it in "the shed"..............I would turn off the fuel while the engine is running at full throttle, to deplete a portion of the fuel in the bowl. 15 to 20 seconds of run time will suffice. Lowering the fuel level in this manner will eliminate the chance of an overfull bowl leaking some fuel into the engine after the engine is shut off. After you have lowered the fuel bowl a bit, you can go ahead and stop the engine the way you have practiced for 16 years. It is recommended that you add a good "fuel stabilizer" to your fuel supply containers during the entire season of use. This way, you always know that stale fuel is not going to be an issue. I also recommend adding a little "upper cylinder lubricant" (used to be A.K.A. "Top Oil") Marvel Mystery Oil is a popular product for this, but not the only thing available. Adding a "capful" of 50:1 two stroke cycle oil to each gallon of gasoline will "do the trick". The "trick" in this case is leaving a very light coat or film of lubrication on the intake valve stem. The intake valve stem is exposed to the air/fuel mix passing through the intake passages on their way to the combustion chamber. As the air/fuel mixture passes the intake valve, some of the gasoline leaves a sticky varnish on the valve stem. If the engine just so happens to stop (shutdown for storage) with an intake in the OPEN position, the built up varnish is apt to hold the valve open ("stuck valve") during the next start up. A stuck valve on start up can lead to bending a pushrod, or allowing a pushrod to jump out of socket. Worst case could be a bent or broken valve or any combination of the above. Just a little "top oil" in the fuel can ward off the evil gremlins of valvestickydom.

Mownie, I was addressing the fuel shut off as a "safety switch" in the belt and suspenders category.

Your original advice got Philsner back in the yard and his current issue is under control.

I enjoy you indepth explainations that are delivered in clear and understandable terms.

Thanks for your support and best wishes, Alan

Thanks Alan, I sorta thought you were leaning that way BUT, I know of a few applications in medium and heavy trucks where a "fuel shutoff solenoid valve" is used, and THOSE, are controlled by a "switch" (the switches are ECM & relays now days). I have also seen some "Dual Fuel engines" (LP and Gasoline) applications that have solenoid valves that cut one fuel supply OFF when the other fuel is selected. These also use a switch to control the solenoid valves. That is why I made the comment I made, I wanted to find out just where you were going with that "safety switch" idea. I even dimly recall a member of this forum bringing up the subject of a 12VDC, inline fuel shutoff solenoid that could be added to any gasoline fueled system to provide "turn key" auto fuel shutoff instead of us having to REMEMBER to turn off the manual inline shutoff valve. And just in case somebody reading this might conclude that the Fuel Solenoid on their carburetor does that, NO IT DOES NOT, it only cuts off the large volume of gas that flows through the MAIN JET (to minimize "afterfire" during engine shut down). Even with the main jet fuel shut off by the de-energized fuel solenoid (during storage), the smaller pilot jet is still open. If the carb float needle valve leaks, the fuel will overflow through the pilot jet and the engine will be "just as drowned" as ever without an inline fuel shutoff valve.

I think its a good idea to go in and clean the carb real good ... ( Even with the fuel shutoff valve in place and being used properly... ). Im not saying he should do it tonight - but I would put it on my to do list.

For example - the cut-off valve is open and the engine is running and the fuel shutoff circuit is opening (and semi closing). but depending on the amount of crud in the carb and how much the circuit doesn't close - I would suspect that he could run rich if the carb starts to overfill on him.

In my recent experiences cleaning out a couple of carbs with the same problem - I opened them and they were *unbelievably* full of crud... the owner never had an inline filter in place. It is very likely that a missing in-line filter will eventually cause the carb's fuel shutoff circuit not to function properly anymore.

Philsner - Do you have a fuel filter on this machine? and if not - you may wish to get one. And you may want to clean out that carb when you have a some time (perhaps at the end of the season).

happy trails - Dave

An 80s model Ford pickup dual tank switch works fine as an electrically operated fuel cut off. Plug the inlet that is open with no power applied. I installed one just because I happened to have it and it has worked flawlessly for a number of years.

A sunny day today and time to cut the grass. The oil level "grew" a bit over the full line on the stick so Ill keep an eye on that and run the engine longer at shutdown (with fuel valve closed) to more fully drain the carb. Everything ran fine.

I have always used fuel stabilizer, and I plan to take Mownies advice and begin using top oil. Seems like cheap insurance and I like cheap. I do indeed have a fuel filter which is long overdue for replacement and Ill swap that out next time I visit the hardware store.

I have never worked on carburetors, though Sears lists a rebuild kit available for mine. I am reasonably handy and think I have common sense. Might be a good off season task. How difficult would the rebuild job be? How difficult to tune the carb once rebuilt?

It's not "rocket science" exactly, but it does require that you be careful about paying attention to how something comes apart. You will often read my suggestions about using a digital camera to record the "tear down" as you go. Take plenty of pictures (it ain't like you gotta take 'em to the drug store for developing any more, you DON'T still do that, do you?). Take pictures from different angles. If you use the digital camera trick to "leave a trail", you won't have any problem going back together. Just imagine how different the story of Hansel and Gretel might have been if they had a digital camera (or camera phone).

More great advice, thank you Mownie.

I tried to crank my lawn mower motor, but it would not start. I took the float out and cleaned it. It was stuck. It appeared that it was getting gas, but wouldn't start for a long time. When it started it would only run with the choke fully closed and would not idle down, but I mowed with it and it worked okay except I could not idle. After that I have not been able to start it. It only backfires through the carbarator and exhaust.

How to install fuel pump to a intek 17 horse briggs that is gravety fed.