Grinding noise/feeling around 6000rpm

[OutofFaze]

Hi guys,

I have some strange behaviour that I'm not sure is normal.

When I pull through the revs and gears, it feels like the engine (I assume) starts grinding at around 6000rpm give or take. I can feel it through the handlebars and it tends to go after about 7000rpm or when I push it way up into the power band its fine too. This occurs worst when im going about 60 mph and keeping the revs in the trouble zone.

I also found that if I potter along at just over 5000rpm it feels really smooth, no vibration or grinding and almost no negative engine sensation at all.

I have a new chain and sprockets (600 miles ago) and a new oil filter and oil change then too (when I bought the bike). In an attempt to improve it, I tightened my chain very slightly today and lubed it and realigned my back wheel because I notcied that the adjustments on the chain tensioner didnt completely match and managed to get them to be almost the same now.

I took the bike out 2 hours after making the adjustments to allow the lube to dry a bit and I feel like it has improved and the rpm range of grinding is narrower now, but still centered on 6k. I will check the engine oil level in the morning just to make sure too.

I have tried to search for this but havent seen anything that exactly matches what I feel.  As an engineer, it makes me cringe because i'm running all kinds of imagination adventures where I visualise too big metal plates grinding swarf into my gearbox haha

Is this well known to you? Any tips?

Many thanks!

James

[Dead Eye]

Are you certain its from the engine? Only reason I ask is that the few rattles and vibrations I've had have been due to the fairings / plastics - last one was the metal cone inside the left hand light housing.

Not really sure on what else it could be as if it was related to the chain / sprockets or front wheel etc I would expect the vibrations / noise to correlate more with road speed and not be related to the RPM of the engine.

If it is the engine I guess it could be something like the water pump, alternator, oil pump etc but this is incredibly unlikely as its very rare to hear of these parts failing.


Oh, actually, something I just thought of - what about the clutch? Have you checked the clutch plates for wear?

[Chris]

I know you say it's connected to engine speed but is it anything to do with the road speed? Possibly the wheel bearings as they can be worse at certain speeds/load.
 
One thing to be careful of is that sometimes the markers on the rear swing arm can be a bit misleading and even if they're set the same the wheel can be slightly out of line but I'm sure you'd feel that through the steering and behaviour of the bike. Might be worth checking another way to make sure the wheels are dead straight. If they have been out of line then this can put extra strain on lots of things but might contribute to the bearings wearing out faster.
 
Hope that makes sense.
 
chris

[limax2]

It is very common for the 600 fazer to have a small vibration patch around 6,000 r.p.m. mark. Sounds just like what you describe, super smooth above about 6,500 and below 5,500. If the carbs are out of balance I guess it could make it worse. I'm assuming the weights are still in the end of the handle bars because you might feel it more without them. It used to annoy me a bit but I must have got used to it because I tend not to notice it anymore.
Nothing to do with the vibration but make sure you haven't over tightened the chain as that will do a power of no good to the gearbox bearing etc. Also it is better to align the back wheel to the front rather than rely on the swinging arm markers as they can be out.

[OutofFaze]

Thanks for the replies everyone.

I'll check the chain again and measure the slack properly.

The sensation is definitely related to engine rpm, as far as I can tell and doesn't seem to matter which gear I am in.

I also wondered if my brakes are dragging on the front, but I don't know why I would only feel that at certain rpm...

I'll keep an eye on it. It's still under dealer warranty (even though I bought it used - Sweden is good!) so if I can't figure it out I'll get them to take a look.

James

[OutofFaze]

For the whole thread, I forgot to mention that it is a 2000 FZS600 Fazer.

Also, it could be normal behaviour to have a rough patch like this and I've heard others describing it too. I just want to make sure I'm not causing damage

[Fazerider]

A long shot, but you don't happen to have a Bridgestone BT021 on the front do you?
It's just that they make a weird abrasive noise on the FZS600 at certain speeds.

[OutofFaze]

Nah, I've got a Michelin Pilot something or other... I looked at that today.

The noise/feeling was much improved today on the way to work but still there. It might be my imagination but I feel that the longer I am on the bike the worse it gets so I wonder if it's related to how much front brake I use, or engine temperature. I don't know really... I have many theories but none with proof

James

[xlewisbdx]

I had a problem where the bike was squeaking and grinding over 30mph. Turns out my front wheel bearings where fucked. Check them.

[darrsi]

I had a problem where the bike was squeaking and grinding over 30mph. Turns out my front wheel bearings where fucked. Check them.

That's the technical term...... 

[xlewisbdx]

I had a problem where the bike was squeaking and grinding over 30mph. Turns out my front wheel bearings where fucked. Check them.

That's the technical term...... 

I'd rather say fucked than disintegrated or not there 

[darrsi]

My first thoughts would've been chain too tight or wrong alignment, but that wouldn't just make a noise around 6000rpm, it would be all the time, and you'd really feel that through your left footrest.
Are your wheels spinning freely enough? A siezed brake piston could cause noises if the pads are being pushed from one side only and remaining stuck in position on the other side?
Check to see if the pads are wearing at different rates either side?
As Lewis also said, wheel bearings could be 'focced' and only prone to making noises at certain speeds too.

[OutofFaze]

Hi guys,


I took the bike back to the shop (they are a Yamaha dealer) because i had read everything suggested here and checked it on the bike, and also some of my own wild theories and couldn't find anything that seemed wrong..


The main mechanic took it for a test ride after hearing the symptoms and how to reproduce it, and came back to say that he couldn't find anything out of the ordinary. So, it seems that not only am I a hypochondriac for my body, but also my bike.


Gonna crawl under a rock and feel silly for a while now.


Thank you very much for all your replies and suggestions, it makes me glad to have joined the forum!


James

[dBfazer600]

James dealers will say nothing is wrong as it cost them to put it right. Get an independent mechanic to check it out and if there are any concerns at least you have a second opinion.
 
Daz

[darrsi]

I had a similar issue when my mechanic refitted my carb rubbers incorrectly so that it leaked air causing hesitation and bogging down on hard acceleration.
THREE of them rode my bike and said nothing was wrong, but the fact is i ride the bike every day and know exactly when all is not well, the same as you know when you're not feeling well yourself.
He could be right, by all means, but it's difficult to pinpoint a nagging problem when riding someone elses bike unless it's fairly obvious.
So i can only suggest keeping your ears open and listen for anything getting louder or more sinister sounding.
Hopefully he's right and it's just general "bike noises". 

[Fazerider]

As this appeared a while after a chain and sprocket change it might be the old sprocket nut problem.
Did you check what thickness nut they used?

[darrsi]

As this appeared a while after a chain and sprocket change it might be the old sprocket nut problem.
Did you check what thickness nut they used?

Possible, but the thing that's throwing me is that he says he can feel it through the handlebars?
Sprocket or chain problems would be blatantly felt first with your left foot.
I would've thought a handlebar grinding feeling would be aimed more at the wheel area, and the only things that rotate are the discs which obviously can touch the pads continuously with caliper issues, or if the wheel bearings are on their way out?

[Dead Eye]

I wouldn't rule out the chain and sprockets due to handlebar vibrations. I just fitted a new front sprocket which has gotten rid of the knock I had (through left footpeg) - I knew this was definitely the reason. But after my test ride, I found the whole bike to be a bit smoother and it was vibrating less around the handlebars as well

In any case, if its engine based then it will have nothing to do with road speed which pretty much rules out brakes, chain, sprockets, wheels etc etc - need to focus more on the block imo

[darrsi]

As Dead Eye mentioned earlier, when you start hearing/feeling the noise keep the throttle steady (and watch out in front of you) and put the back of your fingers onto the left headlight plug that pushes into the bulb and see if it's that making a noise?
Since i changed back to my Quill exhaust, which has a deep rumble tone to it, it caused my bulb to vibrate to the point of being very annoyingly loud.
Different tones of exhaust will make things vibrate at different RPM, and it's a simple thing to rule out so worth a try.

[Mutleyx]

A long shot, but you don't happen to have a Bridgestone BT021 on the front do you?
It's just that they make a weird abrasive noise on the FZS600 at certain speeds.

I have a BT021 on my front and get the weird sound at some speeds, it has been doing my head in as to what it might be, i have changed the wheel bearings and fork seals (one of the dust seals needed doing anyway so whilst i had the forks off i replaced all the seals) and still get the weird noise.
never thought it would be the tyre but you might be right!
I think it sounds worse cos it amplifies the sound through the fairing

[OutofFaze]

Hi again,

It is more of a feeling than a noise to be honest... Last time it happened, I tried to listen for it bit realised I could only hear wind noise in my helmet.

Also, I studied it more and can feel it in the handlebars like I already said, but also feel it in the pegs and the seat. It feels like the engine just starts making more friction at 6k rpm. Also, I definitely found that speed doesn't matter, it is only the revs, because I can feel it in several gears at those revs. 5.5k and down, 6.5k and up feel smooth all the way.

Also, if I am say at 7k and I lift off the throttle slightly so that the revs drop to 6k I think it can feel more pronounced than if I rise up to 6k. I found that very weird.

I'm an acoustic engineer and I had a weird thought that maybe it is something to do with the air intake. It is very possible that the engine draws air at such a speed (at 6k revs) that it corresponds to the resonant frequency of the intake pipe and makes a really weird sensation. Something like a Helmholtz resonance (like when you blow across a half empty bottle and it sounds like a lighthouse, then you can feel the bottle vibrate)... It feels like that sort of thing but because I can't hear anything for the wind noise in the helmet, I can't really confirm. An acoustic resonance would correspond to the gradual build up and tail off at lower and higher revs than 6k... And also the preciseness of the problem.

Also at lower speeds when I can hear more through the helmet, there is a strong sucking sound from the air intakes so I will check if perhaps something is obstructing it in some way, or just normal behavior.

I've checked everything mechanical I can on the bike:

-Wheel bearings (Front and back)
-Chain tension and alignment
-Engine oil level
-Brakes don't stick at all (as far as I can tell from checking the pads and moving the wheels while on the center stand)

There is a rattle in the fairing exactly as described by the headlight but that occurs at other revs and I just pressed the fairing as suggested by the left headlight and it went away... So I'm not worried about that.

I haven't noticed any lag in power because of this though... Just the feeling.. So I dont think that anything is being degraded or broken.

Maybe I'm just too particular, and I guess I could have written a book about these sorts of things with my old XT600E hahaha :-)

Once again I appreciate your help and suggestions guys! Many thanks :-)

James

[xlewisbdx]

Try the front sprocket nut? Fazers have common problems with them.

[Dead Eye]

Well that sounds less worrying at least May be worth checking the Air Filter as you suggest to see what sort of condition it is in or maybe even look at the plastic panels around the air box - if it is the air intake causing the noise these could be vibrating a little against the frame though they should be secured against rubber fittings.

[Fazerider]

I think Limax's opinion, that this is just the standard "rough zone" the Fazer has, is probably the correct one. The engine mass combined with the rubber mounts has a resonant frequency, and when the reciprocating parts hit that range you do feel more of a buzz though the footpegs and bars.
The solution, of course, is to spend as much time as possible above 7000rpm.

[darrsi]

A blocked air filter could create a noise if it's not getting enough air but that would also be felt in performance as well.
How old is the filter?
Next time you change it swap it for a K&N.