Annoying screech!

[ukzknos]

Anybody any views on this one:

exactly from 1750 to 2000 rpm (whilst riding) in every gear I hear an annoying screeching noise.
Must be related to gearbox/drivetrain because it isn't there when stopped.

Thanks

[Bob_Roller]

I'm wondering, if you have something vibrating on the bike, like the centerstand, or exhaust system related, or something else that may be slightly loose, as it happens at a specific rpm range.

[fastcataz]

When was the last time you changed the trans oil?

[montmil]

Are positive it's the gear box? Have you tried the stethoscope trick? Check my Worrisome Noise thread nearby...  I though the big end bearings had gone Tango Uniform but it was the old and original timing chain and tensioner.

Monte

[ukzknos]

Hi Chaps!

I need to resurrect this post because it's driving me mad (and scaring pedestrians)!

I've changed the oil in everything; engine, gearbox, driveshaft and final drive. So I'm confident it's not related to the drive.
It doesn't happen when the engine is running and the bike is stationery so I suspect the clutch, but if so, don't know what it could be?
 :-/

C'mon guys, rack your brains!

[Bob_Roller]

About the only thing that I can think of, is the push rod that activates the clutch.

The forward end of the push rod contacts the diaphragm clutch release spring.

The best I can remember, you can't remove the push rod completely, unless the rear swing-arm is removed, or displaced, or the transmission is removed from the bike.

[nhmaf]

Does it happen when you are pulling in the clutch lever, or when you let the lever out, or does it happen anytime the RPMs are in the range you indicated?

Too bad we can't have you make the sound for us (though I suppose you could record a .WAV file on your PC somehow) - I love it when the
callers do thi for the "Car Talk Guys" - which is a radio call-in show run by a couple mechanics who went to Mass. Institute of Technology on public radio, here in the USA.

[ukzknos]

Just had a thought, prompted by your post nhmaf, it can't be the clutch because it is happening in every gear at this rpm with the clutch disengaged.
Recording the 'screech' whilst riding the bike is too clever for me, so I'll pass on that one!
Maybe my attention should return to something like the timing chain tensioner but...... why so consistently repetitive at 2000 rpm?
 

[Bob_Roller]

I'm not familiar with the 'first generation' '78-'80 R65's, but I remember from visiting Boxerworks.com, that the crankcase ventilation valve is a spring loaded piston type valve, and has been known to emit a 'turkey gobble' type noise, when things aren't right with the valve.

Just thinking out loud here !

You could try shutting the engine off when the noise starts, and see if  it makes any difference.

[ukzknos]

All ideas are potentially good ideas Bob_Roller!

You keep 'em coming and I'll check 'em out  

[Justin B.]

Ride through the range where it screeches, pull in clutch and hit kill-switch.

I'm trying to understand something.  You said it happenes in every gear at the same RPM even if you have the clutch disengaged?  So, does it screech if it's standing still, clutch pulled in, and engine running at that RPM?  It just doesn't make any sense...

I know (from automotive experience) that some vacuum leaks can cause a pretty annoying "whistle" but I don't think these would generate enough vacuum to waste enough on a leak like and keep running decently...

[nhmaf]

I also am trying to understand the conditions that cause it - I was at first thinking that the bearing at the back of the clutch pushrod/piston was failed and screeching as it spun up when the pushrod contacted the diaphragm spring when pulling the clutch lever in, but now it seems that it is purely engine RPM related, so I would thing that it could be reproducible while sitting still - or it may be a combination of vibrations like when the darn heat shield on your car's catalytic converter is loose - sometimes engine RPM alone isn't quite enough to get it to "sing" like it can repeatably do when on the road.

The "turkey gobble" symptom with the crankcase brether valve that I was aware of generally only happens at startup or shutdown, but I guess that too could be RPM related - I've just not heard it before.... hmm, this reminds me I've got to get my turkey hunting stuff together - season starts beginning of May!

[vestandpants]

Ive just stumbled across this post and, yes my '79 did the same thing.

It used to happen when I was going down the gears to take a left hand turn at about 2000 rpm. Now as some of you know on here that I have replaced the gearbox (which was disintergrating) and the clutch (which was well worn) which I suspected either or a combination of the two. I also discovered after I took the bike to bits that the rear wheel bearings were well worn too with virtually no grease  

I test ride it next week and I can tell you then whether I've cured it  

[Justin B.]

The transmission in my '95 R100RT developed a howl in all gears but I wouldn't classify it as a "screech", not even close  It was not RPM related and seemed to be louder in the lower gears.  I replaced it when it was noticeable in 5th gear.

[ukzknos]

Bob_roller you asked in an earlier post whether the noise stops or continues when you hit the engine kill switch?

The answer is 'stops'; I had the bike running at a constant 2000rpm so the screech was continuos hit the kill switch and no screech.
I can't work out what this is telling me though?