Weird Whistling noise on K8 Sport.

[5150]

Hi all,

Bit of a conundrum, this. My K8 Sport emits a whistling noise above 40mph. It sounds like a speeded-up police siren (sometimes two at the same time), and happens in any gear, with or without the clutch engaged, and whether or not I'm using either brake. I can't tell where it's coming from but it definitely seems related to road speed. It's not my lid, either....

It sounds very much like the noise in the video on this thread: http://forums.sv650.org/showthread.php?t=175272

I had a new chain and sprockets fitted about a month ago, but the bike's only been making this noise for a week.

It was due a service anyway so I took it in straight away to see if they could find out what the noise was, and the only thing that arose was that the oil was very low (I know, I know). They couldn't pinpoint where the whistle was coming from.

The words 'output shaft', 'front sprocket bearing' and 'front wheel bearing' were used, not to mention 'replacement engine'.... which is worrying.

I was told that if it's the engine on the way out, I'll definitely know about it in the form of awful grinding noises at some point. But the motor itself sounds as sweet as a nut. There are no abnormal bangs, whirrs, clunks, knocks or rumbles at all - a second opinion from another mechanic confirmed that. It's bugging the hell out of me.... not to mention the mechanic.

Has anyone else experienced an odd noise like this? Any help from the Mighty .Org would be much appreciated!

Try it in the garage on a rear wheen stand run the bike up to 40. See if it whistles if not maybe its the fairing or something. (I accept the engine/gearbox wont be under load but worth a go)
Alternatively go down a steep hill at 40 and put the bike in neutral, clutch in, etc see if it changes. If it was the engine I'd expect it to be rev dependant rather than speed dependant.

[5150]

Originally Posted by Lawman

Try it in the garage on a rear wheen stand run the bike up to 40. See if it whistles if not maybe its the fairing or something. (I accept the engine/gearbox wont be under load but worth a go)
Alternatively go down a steep hill at 40 and put the bike in neutral, clutch in, etc see if it changes. If it was the engine I'd expect it to be rev dependant rather than speed dependant.

Good suggestions - thanks! I did both of those, too.... and still he whistles. The thing is, nothing's changed since the chain and sprockets were done. If I'd been mucking about with the fairings and things, I could see a correlation. But this has just started up out of the blue....

It's definitely related to road speed - although, like you say, the engine and gearbox weren't under load on the paddock stand.

[tigersaw]

I had a mini that made that noise (very different vehicle I grant you). It turned out to be a bearing that partially siezed and was actually spinning the whole thing in the casing once the speed got up

If it still whistles on the stand, remove the chain and see if it still does it. Or if you can, the rear wheel and move the chain off the front sprocket, this could be very dangerous so be careful and try again, it will be a process of elimination i'm afraid.

[5150]

Double post. Oops.

[5150]

A little update: I now have new front wheel bearings, which seemed to do the trick initially - but then the whistle returned, albeit much quieter than before.

I think that probably narrows it down to the front of the bike - the front wheel and brake calipers had to come off to fit the new bearings, of course. So in re-fitting them, something has obviously improved. I reckon we can rule out the engine and final drive, since it's never whistled on the stand, and the only thing that's changed between loud noise and quieter noise is stuff on the front wheel.

Next stop is to change the brake discs and pads (which are starting to need it anyway).

I'll keep this thread updated for anyone else who might have the same problem.... And more suggestions are always welcome! Thanks, everyone....

Thought you said it still whistled on rear stand, I cant see how front wheel bearing would do this if wheels not turning? Good luck with it anyway, nowt more annoying.

[5150]

Hiya,

Nope - it's never whistled on the stand. Quiet as a mouse (apart from the sexy V-twin roar). That was the initial thought, but it only makes the noise when it's rolling on tarmac....

Fingers crossed it won't be too expensive to sort!

[5150]

Just a quick update to this.

I now have new front brake discs and pads, and both calipers had a thorough going-over (one of them wasn't sliding - until the salt and cramp was Dremelled out, anyway).

The right-front disc was very slightly warped, too - I could feel the pulsing through the lever towards the end of its life.

The upshot is that the whistling has stopped. So if anyone has the same noise - and it was exactly like the one in the video - I'd suggest they give their front brake calipers a thorough clean (not just the pistons), check everything moves as it should, and maybe even examine the discs for warpage.

I hope this helps someone!