On Sun, 12 Apr 2009 20:54:49 +0100, Jules13
wrote:


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.

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.



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?

Unlikely.


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?

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.


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