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jim · 21-05-2010, 05:54 PM posted to alt.home.lawn.garden

s wrote:

On Fri, 21 May 2010 07:18:04 -0400, "Joe" [email protected] wrote:

Depends what side the mower is tipped.

wrote in message
...
On May 20, 1:24 pm, jim "sjedgingN0Sp"@m@mwt,net wrote:
wrote:

On May 18, 11:05 am, jim "sjedgingN0Sp"@m@mwt,net wrote:
wrote:

On May 18, 1:49 am, "Bob F" wrote:
Helen4521 wrote:
Can anyone help please? When I was mowing, I ran over a largish
stone.
The mower made a noise like the stone was whizzing around with
the
blades then white smoke came out of the exhaust. When I stopped
the
mower, I tilted it up (only slightly) to see if the stone was
still
underneath, didn't see it but saw score marks where it had
been. The
blades still move OK. When I started the mower again, it
sounded like
a tin can and there was a bit of oil coming out of the exhaust.
Have I
done serious damage? What should I be checking next? The mower
is
only 2 years old.

Pull the plug wire, and rotate the blade. Chances are, you will
find that the
crankshaft is bent, causing one end of the blade to be higher
than the other.

With oil coming out the exhaust after hitting a large rock, you
have
serious damage and it isn't going to be cheap to fix.

That is probably not true. The oil coming out the exhaust is probably
caused by tipping the engine and getting oil into the crankcase
breather
and then sucked into the engine. If the engine is running badly it is
probably because the flywheel key is sheared. Running the engine with
a
sheared key will ruin it. Fixing a sheared key shouldn't cost very
much.

I'd try to get
a rough estimate over the phone on the repair cost range before
spending money on fixing it. If it's a low to mid-range mower, you
may be better off buying a new one and parting this one out on
Ebay.
Start with the engine and tell them you hit a rock and it no longer
runs, all sales final, as is, etc. That usually gets people
interested. I'm amazed at what people will bid on crap like that
on
Ebay.

Except that she said it still ran but sounded like a tin can. I'm not
sure what exactly "sounded like a tin can" means, but a sheared
flywheel
key or the blade hitting some piece of sheet metal might sound
something
like that to some people. Since there was no mention of excessive
vibration I would guess the crankshaft is OK.

-jim- Hide quoted text -

- Show quoted text -

If the oil coming out of the exhaust is due to tipping the mower over
for inspection, how do you explain the white smoke coming out of the
exhaust that suddenly appeared when she hit the rock?

Pretty much the same mechanism. The smoke was the result of a slug of
oil getting through the crankshaft breather. To be any more specific
than that, would require knowing what sort of engine/mower this is. How
would you explain it?

-jim- Hide quoted text -

- Show quoted text -

The poster said she "only slightly tipped" the mower. She didn't
turn it upside down. I've tipped many mowers over on their side and
never had any white smoke come out. In fact, that is how you change
the oil on most of them today. The white exhaust smoke also appeared
right after hitting the rock while the mower was still running and
before turning it upside down. I don't see how hitting a rock,
accounts for oil getting into the combustion chamber, unless something
is broken internally.

Perhaps we'll hear back about how it turns out.

I had a customer come in a couple months ago, kinda the same
situation, except his wouldnt start at all, leaked oil out of the
muffler and carburetor. I went ahead and replaced the sheared flywheel
key, primed it, and fired it up. Smoked lick heck for about a minute,
then cleared up and ran great, no knocks, vibration, ill effects, etc.
Ran a compression check and a leakdown test with great results. I have
seen other mowers, and even a tiller, in the past with the same thing.
Hit something, sudden stop, oil in the muffler and or carb, but no
mechanical damage. All I can guess is a sudden change in crankcase
pressure to the high positive is causing oil to blow past either the
rings or valve guides and blow out both ends...kinda like when you
cough and f@rt at the same time.....it happens....Midnite

Yeah that sounds typical, but I still say any oil that ends up in the
muffler got there by getting into the intake through the breather. The
same inertia that will shear the flywheel key (and/or bend the crank)
will toss the crankcase oil where it normally doesn't get tossed.

-jim

nuevolawnandgarden at verizon dot net
nuevolawnandgarden.webs.com