Re: Front end 'clunk', headstock bearings?
 

People like to think when they mod their bike it has made it better.

Besides, I doubt many of those people changed just the oil, they probably changed the spring for a heavier one too, so the fork was less likely to compress as fast, and so less likely to create the hydraulic lock. IMO the oil needs to be matched not just to the damper rod, but to the spring as well, and that's the problem with the stock SV, the spring is too soft.

I put too thick an oil in mine because I hadn't checked the cst@40 rating. Funnily enough lots of threads said it was the right oil to use! ;-) The clonk got much worse, to the extent that it would do it going up or down the dropped kerb into the driveway. It wasn't travel as I had a tie wrap on the fork to measure that.

If somebody can give me a plausible explanation I'm all ears, but I'm the only person on this thread offering one. There's one thing for sure, something causes it, and it's not bottoming out and it's not a paranormal phenomenon. ;)

Re: Front end 'clunk', headstock bearings?
 

Thicker oil made mine more prominent.
Your noise don't follow the norm.

Re: Front end 'clunk', headstock bearings?
 

I don't know what makes it do the clonk, I don't think it is cavitation/hydraulic lock as there is no reason for flow to make a knock when it is subjected to pressure, there is no compressibility to cause the knock when this is released.
My best guess is it is the vertical clearance in the damper rod seal allowing the seal to knock up and down.

Pointy has a different rod design, bit less clearance, bit less knock. Perhaps.


If it is worn fork bushings you would feel this when rocking.


We fixed it on your though :-)

Re: Front end 'clunk', headstock bearings?
 

You've changed your mind on that one then. It was you that sent me off reading a paper on 'oil flow through a sharp edged orifice' when WE came up with that explanation for it.

Re: Front end 'clunk', headstock bearings?
 

I can say if wind off the preload the clonk is louder. So it's tightening up somthing in there.

Re: Front end 'clunk', headstock bearings?
 

It is that sort of flow, there is still a limit on how much you can flow through, but I don't think that's the knock.

I believe last time we talked about this it was about the poor comp behaviour of a simple orifice damper as it obeys a ^2 relationship.

Re: Front end 'clunk', headstock bearings?
 

bit of an old post to regurge, but was just surfing the old posts to see about headstock bearings on my curvy, as recently theyve started to clonk over bumps pot holes etc.

Wierd thing is, its never done it in the past 3 years of ownership, but I changed the oil in the forks, for the standard grade, then about 3 weeks later it started clonking :confused:

If they all do it, why did mine never clonk before, and has an oil change brought on the clonk, passed its mot recently and wasnt commented on, no obvious free play, can only detect it riding the bike and its really horrible!

Lee

Re: Front end 'clunk', headstock bearings?
 

Haven't you answered your own question? The standard grade is known to make the noise & that's what you've put in. Different grade oil previously in there?

Re: Front end 'clunk', headstock bearings?
 

32K miles worth of the thinnest brown tea youve ever seen :mrgreen: but the clonk didnt happen straight away, took about 3 weeks of daily use before it became apparent.

Re: Front end 'clunk', headstock bearings?
 

what about vertical play on stanchion bushing? may it be related?