Can you guess the knocking on my SV?

I've have a knocking on my SV that can be felt though the handle bars, foot pegs and seat.
I normaly notice it at about 70 mph, making a distinct knock knock, about every half second. This eases off as I slow down, if I go above a ton then it vanishs altogether (or becomes constant).
So what is it?

1. Warped disc's?
2. Buggered chain?
3. Stuffed head bearing?
4. Nackered wheel bearings? front/rear both?
5. Worn swing arm bearing?
6. Something wrong with my calipers?

Originally Posted by Grinch

I've have a knocking on my SV that can be felt though the handle bars, foot pegs and seat.

I think the first thing I personally would be looking at is the rear tyre - just to make sure the tread is all there, and that there isn't some nasty thing stuck in it. Then I think I'd be having a look at the rear wheel bearings - particularly if you've been running the chain tighter rather than looser.

My experience is that the chain, when knackered, doesn't necessarily give you a regular and distinct knock - more like a real rough feel all the time.

But you can also get some odd-ball things like, if the rear brake has seized on, before the pads wear down you get a very hot disc which can heat up the rear wheel bearing and accelerate wear - as well as distort the disc. So you may need to look very carefully at the whole back end - and for my money, that's where it's coming from. (also see my pm).

Some of the other guys probably have much better knowledge of this than I, but I hope this will give you a start.

[northwind]

At 70mph the rear wheel and chain are spinning pretty dang fast so it's not a simple once per revolution knock, that's for sure. So personally I'd rule out chain, tyre and discs entirely, at least as long as you've got any other suspects. (wheel etc would generally knock once every 180cm or so, and chain about a third as often.) And there's no reason an intermittant one would be that regular that I can think of.

But I don't have any alternatives for you Notchy swingarm bearing maybe, but that's a total guess. No chance it's engine derived, ie a slight cough or misfire?

Originally Posted by northwind

No chance it's engine derived, ie a slight cough or misfire?

That's a really good thought!

Originally Posted by El Boccadillo

That's a really good thought!

Its not the engine thats for sure its just not the same, I was thinking the wheel bearings due to them spinning in side the wheel. So when the wheel has done a revolution the wheel bearings are only a quater round? Or have I got my understanding of this wrong?

Dodgy wheel bearings tend to make a droning noise, or even graunching if really f*cked - you'd know it.

[northwind]

Originally Posted by Grinch

So when the wheel has done a revolution the wheel bearings are only a quater round? Or have I got my understanding of this wrong?

Eh, something like that. Halfway I think, but it wouldn't be quite that simple. 'sides, worn bearings would be noticable with wheel play most of the time. You should still get the knock at least once every 10 metres or so, probably more like every 6, and at 70 you do that something like 4 times a second, so your bump should be far more frequent than you're getting. Wheel bearings don't really bump either- bearings that don;t turn fully like head bearings etc get notchy, wheel bearings get loose and grindy.

Thing is, i can't think of anything that would be spinning at that speed... This is a job for Sid Squid

Could it be the head bearing then?

Originally Posted by Grinch

Could it be the head bearing then?

<gulp> Hope not fella

Originally Posted by Cloggsy

<gulp> Hope not fella

err why not.....? is there something I should know?