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Hi Bob,
I believe you, of course, but I have never heard this before. I have a
Craftsman 21" walk behind and I usually sharpen the blade and do
maintenance this month, so I think I will see if the engine will fire with
the blade removed for sharpening.
For this to make sense to me, there would need to be some sensor on the
blade, or they are using iron mass of the blade as part of the inductance
field to signal the position for coil firing. The aluminum sump of the
motor protrudes through the steel deck of the mower, so I suppose it is
possible. There is quite an air gap between the blade and the sump of the
engine, however.
You have me very curious and I will let you know if the mower will fire
without the blade attached (if it does, I will not let it run as it is hard
to predict what would happen without that flywheel attached to the
crankshaft).
best,
doug
On Tue, May 18, 2021 at 5:35 PM Bob Spidell <bspidell@comcast.net> wrote:
> Possibly of some interest: I had a Craftsman walk-behind that quit runnin=
g
> suddenly. I tore the engine down, didn't find anything, then finally took
> it to a repair shop. They told me the blade had a crack in it that caused
> the problem; supposedly the blade is part of a timing loop that fires the
> spark. Sort of makes sense if you think of the blade as a flywheel with a
> position sensor on it.
>
> Bob
>
> On 5/18/2021 2:55 PM, Brian and Wendy Warrick wrote:
>
> I run Snapper walk behind mowers and have never gave it a thought. I can'=
t
> see why it would matter. If it did, they would have designed the adapter
> differently.
>
> Brian
> Nampa, ID
>
> ------------------------------
> *From:* Shop-talk <shop-talk-bounces@autox.team.net>
> <shop-talk-bounces@autox.team.net> on behalf of Karl Vacek
> <stearman809@gmail.com> <stearman809@gmail.com>
> *Sent:* Tuesday, May 18, 2021 3:52 PM
> *To:* 'shop-talk@autox.team.net' <Shop-talk@autox.team.net>
> <Shop-talk@autox.team.net>
> *Subject:* [Shop-talk] Mower blade orientaaion relative to piston
>
>
> Last time I sharpened my 21=E2=80=9D walk-behind mower blade I thought of
> something that=E2=80=99s never occurred to me, after using the same brand=
of mower
> for 25 years..
>
>
>
> On a Snapper, the blade can actually go on any way onto the square adapte=
r
> keyed to the crankshaft. The mounting point is square, no pins, no longe=
r
> side, nothing.
>
>
>
> One way would be aligned with the cylinder at TDC/BDC, and the other way
> would be across. It=E2=80=99s been off many times and there=E2=80=99s no=
way to tell how
> it was mounted originally. The manual is silent on this.
>
>
>
> Power stroke shouldn=E2=80=99t matter, but maybe some dynamic issue one w=
ay or the
> other?
>
>
>
> Thanks!
> Karl
>
>
> _______________________________________________
>
> Shop-talk@autox.team.net
> Donate: http://www.team.net/donate.html
> Suggested annual donation $12.96
> Archive: http://www.team.net/pipermail/shop-talk
> http://autox.team.net/archive
>
> Unsubscribe/Manage:
> http://autox.team.net/mailman/options/shop-talk/dirtbeard@gmail.com
>
>
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<div dir=3D"ltr">Hi Bob,<div><br></div><div>I believe=C2=A0you, of course, =
but I have never heard this=C2=A0before.=C2=A0 I have a Craftsman 21" =
walk behind and I usually sharpen the blade and do maintenance=C2=A0this mo=
nth, so I think I will see if the engine will fire with the blade removed f=
or sharpening.</div><div><br></div><div>For this to make sense to me, there=
would need to be some sensor on the blade, or they are using iron mass of =
the blade as part of the inductance field to signal the position for coil f=
iring. The aluminum sump of the motor protrudes=C2=A0through the steel deck=
of the mower, so I suppose it is possible. There is quite an air gap betwe=
en the blade and the sump of the engine, however.</div><div><br></div><div>=
You have me very curious and I will let you know if the mower will fire wit=
hout the blade=C2=A0attached (if it does, I will not let it run as it is ha=
rd to predict what would happen without that flywheel attached to the crank=
shaft).</div><div><br></div><div>best,</div><div><br></div><div>doug=C2=A0<=
/div></div><br><div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_a=
ttr">On Tue, May 18, 2021 at 5:35 PM Bob Spidell <<a href=3D"mailto:bspi=
dell@comcast.net">bspidell@comcast.net</a>> wrote:<br></div><blockquote =
class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px sol=
id rgb(204,204,204);padding-left:1ex">
=20
=20
=20
<div>
Possibly of some interest: I had a Craftsman walk-behind that quit
running suddenly. I tore the engine down, didn't find anything, the=
n
finally took it to a repair shop. They told me the blade had a crack
in it that caused the problem; supposedly the blade is part of a
timing loop that fires the spark. Sort of makes sense if you think
of the blade as a flywheel with a position sensor on it.<br>
<br>
Bob<br>
<br>
<div>On 5/18/2021 2:55 PM, Brian and Wendy
Warrick wrote:<br>
</div>
<blockquote type=3D"cite">
=20
=20
<div style=3D"font-family:Calibri,Helvetica,sans-serif;font-size:12pt=
;color:rgb(0,0,0)">
I run Snapper walk behind mowers and have never gave it a
thought. I can't see why it would matter. If it did, they would
have designed the adapter differently.</div>
<div style=3D"font-family:Calibri,Helvetica,sans-serif;font-size:12pt=
;color:rgb(0,0,0)">
<br>
</div>
<div style=3D"font-family:Calibri,Helvetica,sans-serif;font-size:12pt=
;color:rgb(0,0,0)">
Brian</div>
<div style=3D"font-family:Calibri,Helvetica,sans-serif;font-size:12pt=
;color:rgb(0,0,0)">
Nampa, ID</div>
<div>
<div style=3D"font-family:Calibri,Helvetica,sans-serif;font-size:12=
pt;color:rgb(0,0,0)">
<br>
</div>
<hr style=3D"display:inline-block;width:98%">
<div id=3D"gmail-m_-6852136761353026904divRplyFwdMsg" dir=3D"ltr"><=
font style=3D"font-size:11pt" face=3D"Calibri, sans-serif" color=3D"#000000=
"><b>From:</b>
Shop-talk <a href=3D"mailto:shop-talk-bounces@autox.team.net"; t=
arget=3D"_blank"><shop-talk-bounces@autox.team.net></a> on behalf
of Karl Vacek <a href=3D"mailto:stearman809@gmail.com"; target=
=3D"_blank"><stearman809@gmail.com></a><br>
<b>Sent:</b> Tuesday, May 18, 2021 3:52 PM<br>
<b>To:</b> '<a href=3D"mailto:shop-talk@autox.team.net"; tar=
get=3D"_blank">shop-talk@autox.team.net</a>'
<a href=3D"mailto:Shop-talk@autox.team.net"; target=3D"_blank">&=
lt;Shop-talk@autox.team.net></a><br>
<b>Subject:</b> [Shop-talk] Mower blade orientaaion relative
to piston</font>
<div>=C2=A0</div>
</div>
<div lang=3D"EN-US">
<div>
<p style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:=
Calibri,sans-serif">
Last time I sharpened my 21=E2=80=9D walk-behind mower blade =
I
thought of something that=E2=80=99s never occurred to me, aft=
er
using the same brand of mower for 25 years..</p>
<p style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:=
Calibri,sans-serif">
=C2=A0</p>
<p style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:=
Calibri,sans-serif">
On a Snapper, the blade can actually go on any way onto
the square adapter keyed to the crankshaft.=C2=A0 The mountin=
g
point is square, no pins, no longer side, nothing.</p>
<p style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:=
Calibri,sans-serif">
=C2=A0</p>
<p style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:=
Calibri,sans-serif">
One way would be aligned with the cylinder at TDC/BDC, and
the other way would be across.=C2=A0 It=E2=80=99s been off ma=
ny times
and there=E2=80=99s no way to tell how it was mounted origina=
lly.=C2=A0
The manual is silent on this.</p>
<p style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:=
Calibri,sans-serif">
=C2=A0</p>
<p style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:=
Calibri,sans-serif">
Power stroke shouldn=E2=80=99t matter, but maybe some dynamic
issue one way or the other?</p>
<p style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:=
Calibri,sans-serif">
=C2=A0</p>
<p style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:=
Calibri,sans-serif">
Thanks!<br>
Karl</p>
</div>
</div>
</div>
<br>
</blockquote>
<br>
</div>
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et=3D"_blank">http://www.team.net/donate.html</a><br>
Archive: <a href=3D"http://www.team.net/pipermail/shop-talk"; rel=3D"norefer=
rer" target=3D"_blank">http://www.team.net/pipermail/shop-talk</a> <a href=
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<br>
</blockquote></div>
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Archive: http://www.team.net/pipermail/shop-talk http://autox.team.net/archive
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