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NotTaR of small Gasoline Engines and Rotary Lawn Mowers : About squeals and other animal noises
Copyright ©
1994-2007, Samuel M. Goldwasser. All Rights Reserved. Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied: 1. This notice is included in its entirety at the beginning. 2. There is no charge except to cover the costs of copying.
I may be contacted via the Sci.Electronics.Repair FAQ (www.repairfaq.org) Email Links Page.
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While some may describe the engine of an antique automobile as 'purring', this
will not likely apply to most gasoline powered lawn mowers. It would seem
that noise reduction is just not a high priority design issue with lawn mower
engineers or marketing types. However, even if not exactly quiet, the sound
made by a healthy mower should not be similar to that of a pig being tortured.
- A screeching or squealing sound may be the result of worn bearings or
inadequate lubrication. This could be due to lack of oil (!!) or a problem
with the oil distribution system (pump, passages, slinger, etc.). It could
also be a problem with auxiliary mechanical parts - power take-off, front
wheel drive, or a starter clutch that fails to disengage.
- Banging or rattling noises may be due to parts that have worked loose due
to vibration or by being inadequately tightened (by someone else, of course).
The entire engine may be bouncing around on its mount. Or, the flywheel,
blade, attachments, or chassis parts may be vibrating. Even if everything
appears secure, there is quite a bit of energy associated with an engine
running full throttle and parts can work loose.
- A low frequency shuddering or vibration may be due to debris under the
deck. Check for wads of matted grass, twigs, branches, and 3 foot logs,
caught in the baffles or exit chute. Sometimes, globs of this stuff fall off
and get slung by the blades with all sorts of associated strange sounds.
A combination of the above are also possible. For example, a loose flywheel
could result in it scraping against the magneto yielding a sound like a cat
being squeezed to death (or that of a first year violin student) but possibly
only at high revs :-).
Of course, a badly worn engine can also result in piston and rod slap and
other mechanical noises as internal parts with excessive clearances whack one
another. A complete engine overhaul may be in order or just tolerate it and
plan for a new mower when the final day arrives (or your neighbors take up a
collection).
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