Strange Engine Noise

ryuiucJuly 1, 2010

Ive got a 18.5 HP -42" riding mower that is making a terrible noise. While mowing I ran over a small branch that somehow managed to get above the deck and push the blade belt off one of the pulleys. Immediately I heard a knocking noise from the engine and I shut everything down. Upon inspection I saw the displaced pully but everything else looked fine so I went ahead and alligned the belt where it should have been. After restarting I continued to mow and managed to finish off my lawn just fine but the engine was still not sounding right and this is even when the blades are not engaged. Im not sure if something else is off aside from the belt I fixed or if the belt is not tensioned properly anymore (although the noise is present without the blades being engaged). Not sure how to describe the sound other than like a hollow metal knocking noise that is coming right from the engine. Any ideas on what could be going on?

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walt2002

You need to post the model number of your engine as there is more than one 18.5 hp B&S engine and they are drastically different.

Walt Conner

    Bookmark   July 1, 2010 at 4:19PM
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ryuiuc

I believe its a 18.5 HP* LT 42 Tractor. 18.5 HP Briggs & Stratton® OHV Engine with Oil Filter

Bought from Tractor Supply Co. about 5 years ago.

    Bookmark   July 1, 2010 at 4:38PM
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rcbe(6)

you'll need to look closely at the sheet metal on your engine - will find either a decal/plate with model/type info or the info will be stamped into the shroud sheet metal.

    Bookmark   July 1, 2010 at 5:20PM
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mownie(7)

Look on the engine itself to find 2 critical numbers.
The model number and the type number.
Look at the example photo below.
Yours might appear to be a little different in style but it will have all the numbers as in the example.
Need model and type number.

    Bookmark   July 2, 2010 at 1:20AM
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wheely_boy

Maybe you can't find the model and type number because the connecting rod broke it off the side of the engine??

    Bookmark   July 2, 2010 at 5:54AM
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mownie(7)

Considering the circumstances (all of them) I suspect that during the de-railment of the belt, a chunk of material was torn off the ground drive belt (transmission). Now, as the gapped belt section passes each V-groove pulley.......it produces a bang or thud. It is not uncommon for a belt (or pieces of a broken belt) to be thrown from the pulleys of one system..........into the belts of another system, causing a cascade effect of damaged parts in the other system.
The fact that the noise persists even when the deck is not engaged is what sort of points to a chunk of material missing from the "V surface" of the transmission belt.

    Bookmark   July 2, 2010 at 10:43AM
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walt2002

OR something got wedged in the V of the engine drive belt pulley. Got a service call once and there was part of a Hickory Nut shell wedged in the pulley.

Walt Conner

    Bookmark   July 3, 2010 at 8:27AM
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rcmoser

I would also take a close look at the belt (if you haven't replaced it) and the wedge alignment key on the crank. Is this thing manual clutch or elect.?

    Bookmark   July 3, 2010 at 9:38AM
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