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REF: Tools - 108

Stethoscope (and other listening devices)

See also Using a Stethoscope or Other to Hunt Down Engine Noises in the REF section of the Sportsterpedia.

Normally, you'd use all of your senses on an engine. 1)
Look at it, (oil leaks ?, obvious bad signs).
Listen to it, (both with and without a stick).
Feel it, (try a broken crank one time!).
Smell it, (bad gas or oil?).
But like anyone diagnosing things, experience gives you the ability. It just takes time.

The “sounds” in a Sportster engine can be quite disturbing, very much like the engine is going to blow up. 2)
Literally like a tin can of marbles.
What you need to do is to determine if it is the normal sound or if something is wrong.
It is very difficult, almost impossible, to isolate the source of a noise while riding.

There are pros and cons (as in other subjects) to using this listening method.
Sound, and it's interpretation, is a totally subjective thing.
What 'sounds' bad to one doesn't to another.
You'll here noises from all over the engine. 3)
The trick is being able to decipher which ones come from where and if they sound correct or not.
Unfortunately, experience is the best teacher here and you do need a known good engine as a reference point.

However, this method can be used to hear differences in moving parts in the engine.
Using a stethoscope is an excellent way of comparing similar areas, such as lifters, pushrods, etc. 4)
A slightly tight valve train won't make the same sound as a properly adjusted valve.
But it's readily apparent when using a stethoscope. Same for rocker arms.
A quick probe around with a stethoscope now and then alleviates some worry about what might be missed otherwise.
The 'scope' is just another tool to find the general area of the noise.
And there is nothing wrong with using all the tools at your disposal to diagnose and troubleshoot.
It still can be difficult to nail down the exact cause of the noise without visual inspection of the parts.
When you first try it, you're likely trying to pinpoint the source of a particular sound to isolate the area you'd need to disassemble.
But, in some instances, it can be like chasing ghosts by trying to do this with a stethoscope.
The unfortunate reality is that you'll have to break the motor down into 'sections by section' to track down what's ailing it. 5)
That's a hard pill to swallow if the noise you hear is not detrimental by nature.

Or, bite the bullet and take it to an experienced wrench with enough experience to at least narrow things down a bit.
But that may also be a subjective opinion.

This method is also good for detecting air leaks.


Mechanic stethoscope. 6)
The black partition at the end of the tape measure is where the diaphragm is. Note the size of the diaphragm.

Rubber Hose

This can be a spare piece of oil line or even a cut off piece of garden hose.
Hold one end up to your ear and the other end against the testing site.

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