Tech Tips

Diagnosing Preliminary Engine Failure

Written by  September 30, 2007

In previous articles I have covered common maintenance items and discussed preventative measures we should take to make our motorcycles run at peak performance and save us dollars at the gas pump and repair shops. In this article I will discuss a few things to look for in order to diagnose preliminary engine failure.

Trying to recognize the sounds an engine makes when parts are beginning to fail can be very difficult, and hard to diagnose if you have never been exposed to this area. Often times, common valve train noise can be interpreted as a suspected part failure when it really is actually quite normal. Sometimes, being overcautious may give you a false diagnosis that leads you in the wrong direction.

When your motorcycle has a knocking or clicking sound, or any other kind of noise that just doesn’t seem quite right, do you immediately call your local shop or try to diagnose the failed part? The answer to that question will determine your ability to diagnose engine problems. Should you decide to tackle this task, there are several tools you may already have in your possession that may be rather crude but effective! Long screwdrivers and Stethoscopes are vital tools that can get you very close to the problem.

Some motorcycles have rough sounding engines which is the nature of the beast! In some bikes, what may sound like an internal knock may be simply the clutch basket. This noise may be reduced by simply pulling the clutch lever in and listening for any engine change in sound. What may sound like a connecting rod bearing “knock” may be carburetors that are so far out of synchronization that the pressure entering the intake tract is lower or higher among the cylinders. This causes a knocking sound you will swear is the crankshaft.

Under certain circumstances, similar engine noises cannot be diagnosed without removing the engine cover to gain access into the heart of the problem area. When you have found where the problem is, you can address it how you see fit. One other thing you can do to narrow down potential engine problems is to remove the oil filter (spin-on canister) and cut it in half with a hacksaw; or if it is an internal paper-type, you can cut it in half with a sharp knife. This gives you a view of what is really going on inside the motor. The spin-on oil filter is common on most Harley-Davidson models and is becoming popular on many metric bikes because this type of filtration works well.

Crankshaft plain bearings can also be checked by observing the color of the metal shavings you find in the oil filter or oil. Both Babbitt style and plain type bearings have their own distinctive type of shaving. If you find this type of metal in the oil or filter, rest assured the engine needs to be torn down and inspected for damage. The use of this type of engine design is very common these days so play it safe by changing the engine oil faithfully and always inspecting the used oil for metal chips usually found at the bottom of the container. They can be easily identified.

When it comes to looking at the condition of your engine without the total removal and tear down of the engine itself, you have several ways to listen, test, and check the overall condition and get a sneak peek of what’s happening inside.

B-safe out there!

Dave Miller