Sounds like a valid experiment. Can you guys compare notes to see if your
machines are more or less the same age?
Running without the blade out not to be an issue. The engine should have an air
vane governor...
â??
Tom Coradeschi
tjcora@icloud.com
> On 18 May 2021, at 10:38 PM, old dirtbeard <dirtbeard@gmail.com> wrote:
>
> 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 running
> 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> on behalf of Karl Vacek
>> <stearman809@gmail.com>
>> Sent: Tuesday, May 18, 2021 3:52 PM
>> To: 'shop-talk@autox.team.net' <Shop-talk@autox.team.net>
>> Subject: [Shop-talk] Mower blade orientaaion relative to piston
>>
>> Last time I sharpened my 21â?? walk-behind mower blade I thought of
>> something thatâ??s 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 adapter
>> keyed to the crankshaft. The mounting point is square, no pins, no longer
>> side, nothing.
>>
>> One way would be aligned with the cylinder at TDC/BDC, and the other way
>> would be across. Itâ??s been off many times and thereâ??s no way to tell
>> how it was mounted originally. The manual is silent on this.
>>
>> Power stroke shouldnâ??t matter, but maybe some dynamic issue one way or the
>> other?
>>
>> Thanks!
>> Karl
>>
>
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