Engine squealing noise

Greetings everyone. I have been lurking for several months and have put to good use the jetting advice offered by JD, Clark and others.

While woods riding this past weekend in southern Oregon, my '01 WR426 began making a squealing/screeching (bearing?)noise from the engine at 1/3 or greater throttle opening. Putting pressure on the clutch lever did not change the noise at all. The noise is audible in every gear and is definitely load related, not RPM or speed sensitive.

Suggestions anyone?

Oil is changed regularly with Castrol Actevo 10w/40 synthetic blend. Engine is unchanged except for YZ cam timing and revised jetting.

Thanks for your input.

I would drain the oil while warm, and then run a powerful magnet through the oil. Or, dump the oil through a pantyhose or other kind of fine strainer, and see what comes out. If it's bronze (plain bearing stuff), you're in for some cash, if it's silver (metal shaving), ditto. Either way, it doesn't sound good. :)

That noise sounds like a dry front wheel bearing....I would check that before I did anything drastic. A dry bearing squeel will travel back up the forks and sound like a bad water pump.

Bonzai :)


If it were a front wheel bearing noise, it would not come and go while changing throttle opening at the same speed. It would also not go away when I shut the engine off.

Thanks anyway!

I hate to ask but did you make sure the cam locater half rings were in the cam caps during reinstallation? I have dropped my down the cam chain cavity before and had to fish them out.

Did you try the screwdriver at the ear stethoscope? It will help you to isolate the source of the noise.

To start with you will want to drain oil and closely inspect what or how much metallic shavings you have in your filter.

For a closer visual you can :

Remove mag side cover as well as clutch side cover. You could even take it a step further and remove the magneto and then on clutch side the counterbalancer. This will alow you to check out the counterbalancer bearings and have a peek at your crank also. Good time to remove / inspect the clutch as well.

With the clutch cover off you will be able to ascertain the condition of the water pump bearing also.

Hopefully it's something on the exterior of the cases.

Good luck and work patiently! :)


I warmed the bike up and drained the oil into a clean pan and then strained the oil through a clean white cloth. All clean! The magnetic drain plug had no debris attached.

I checked the filter and found some flakes that look like aluminium. the quantity was less than is typical for a first oil change.

While warming the bike up, per SFO's suggestion, I tried the "Ear-o-scope" with a screwdriver but could not determine which side had the most noise amidst all the normal YZF clatter.

RE: dropped cam retainer - been there, done that :) (with my 99 WR 400) so I was very careful when I did the cam timing/valve adjust on this bike, over 500 miles ago.

Tomorrow I will wash the rest of the mud off the bike and take the clutch cover and side cases off and see what I can find.

Thanks for the input.

Fortunately, I was wrong!

What I interpreted as a squealing bearing type engine noise was solved with a couple blows from a rubber mallet before I removed the side cases.

While contemplating my dilemna and examining the bike over a couple of cold Full Sail IPA's, I noticed a small amount of soot around one side of the rear lip of the silencer can / spark arrestor junction.

After one of my failed attempts at a long, steep, hillclimb last Saturday, I had drug the bike around on its right side to get it pointed downhill. This had slightly bent the endcap of the stock silencer and allowed just enough air leakage at large throttle openings to make a VERY loud whistling noise.

Case solved!

Thanks for the suggestions.

the next IPA is on me! :)

Something else to add to the Believe It or Not files....

Glad you figured it out....

Bonzai :)

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