Have I Killed My Friends Petrol Mower?

Hi, hoping someone can help me to establish whether I really have knackered my girlfriends expensive lawnmower !!
its a Briggs & Stratton Sprint 40, which I'm fairly sure is 4 stroke
There's all sorts of prelude to this, but suffice to say that the lawnmower is new-ish, was recently serviced and running fine til this incident.
I turned the mower on its left side, so that the spinning blade was visible, not noticing at the time that this was the side of the exhaust outlet. It ran normally for a while, but then billowed white smoke from the exhaust.
The gap between the exhaust and its guard may or may not have allowed sufficient room for escape of gases. I know for a moment i had a very small fire on the lawn there.
Also a reasonable quantity of engine oil had obviously been expelled from the exhaust. I believe that oil out of the exhaust is very serious indeed.
It sounded normal til it cut out and did restart once, the smoke beginning to die off til it cut again after about 30seconds and it will now not restart.
I fear that perhaps the engine was starved of oil; perhaps the pick up is on the side of the sump that gravity had taken the oil away from? Would I normally have heard knocking from the main bearings if that was the case though? And would it more likely have seized? (its not seized)
Or might the constriction to the exhaust have burnt out an exhaust valve?
I used to dabble in mechanics to cars, most ambitiously on one occasion completing a head gasket job (after much trial and error).
How simple are these engines? What is it the most likely problem with it from the above? Is it a foregone conclusion that the only realistic thing to do is bin the mower?
The spark plug is clean by the way, and the engine turns over and fires normally on a pull, without starting.
Advice much appreciated
Thank You
--
Jules13


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This is a joke, right... nobody, but NOBODY is so dumb to lay a running mower on it's side.... too bad the petrol didn't ignite and incinerate you. Does your girlfriend realize that you should be institutionalized? I'm positive there will be one of those macabre lawnmower slasher horror movies based on your life: "Jules 13th". hehe
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On Sun, 12 Apr 2009 20:54:49 +0100, Jules13

You turned the mower on its side WHILE RUNNING?! For how long? In a four-stoke engine the proper amount of oil may not get to the engine, as it is likely gravity fed. With a lack of lubrication, you may get engine burn with a blue-white smoke and a charateristic odor--not good.

Unlikely.
Hopefully you just have a flooded engine. Wait 30 minutes and try again. Too many pulls (attempts to start) on full choke can flood an engine too. Check the oil on level ground. Check the fuel lines for clogs, bent shaft, dirty carb, etc.

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wrote:

Fires normally on a pull without starting ??? I'm not a lawn mower mechanic, but couple of usual things....
You turned it on the side....while running... that's a heck of a dumb thing to do, but you already know that.
Oil would have passed the rings... gone into the cylinder... that's the smoke you saw coming out of the exhaust. You might have run out of fuel or created vapor lock in the fuel system....
Couple or two things you could try...
Make sure you have sufficient oil in the sump
If you have a spark tester... check for spark. If you don't have a spark tester, you might wish to try an insulated tool to hold the cable about 1/4 inch from the plug... This might take two people... one to hold the cable, the other to pull the rope. Do NOT ground yourself in ANY way to the mower while trying this. You'll know soon enough if you have spark.
Turn it over a few times with the spark plug out. Place finger over hole while turning over.... you should feel a moderate amount of compression, If your finger is covered with oil, you probably would want to turn it over a few time to clean the oil out.
Removing air filter... try spraying engine start, or even a little gas into the carb.. choke open while spraying, close choke. Try to start.
A seized engine will not rope start easily... Bearing knocks are pretty obvious IF it starts. You might just have too much oil in the upper cylinder preventing it from starting.... or you might have burned a valve.
A lot of engines have a grounding switch which prevents engine from starting when safety handle is not depressed. You might have knocked off the spring... so the grounding switch is not released.
Just a few of the things you could try...before discarding the mower....
Peter
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On Sun, 12 Apr 2009 20:54:49 +0100, Jules13

Assuming this is not a troll - GOD, YOU'RE STUPID! 1 - buy a replacement mower; 2- end relationship now to save your girlfriend the trouble after you blow up/burn down the house.
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