Could it be the knocking is there all the time you're braking, but too lightly to notice at first?
Have you tried braking hard straight away (as hard as is safe), instead of the 'normal' way, like doing an emergency stop?

From your description, it sounds like the knocking only starts once you've got a bit of heat into the brakes, you need to do a fairly 'hard' stop on 'cold' brakes to clarify it.

Well, tomorrow i will replace front wheel bearings

A test ride, while in various breaking situations will show if it's ok or not.

If this fails to "cure" the problem, i will re-tighten headstock bearings.

Again, test ride.....and hope this gets it fixed.

I have tried emergency stopping. The problem appears at the end of breaking as i am coming to a final stop.

I believe it's the headstock bearings that need to be re-tightened (from the sensation that reaches my hands) It feels as the stem vibrates inside the headstock. But, since my mechanic spotted play on the front wheel bearings, i will start with this.

No, it is not all the time there and i think heat is not the cause. The front break system is rather "new" genuine 2 years old front rotors, CBR600 front calipers in excellent condition, CBR900(sc33) m/c in excellent condition too, 2 years old goodridge brake lines, new genuine pads, fresh dot 4 brake fluid.

Replacing the whole front braking system has cured a bit the problem. Using the original brake setup the problem was more intense.

Two years back, i also replaced the headstock bearings with genuine ones (seals too). Maybe they have not bedded properly.

Thank you all for taking the time to help!

I will take your advise and come back with results.......

I would say from your description that it would have to be something that's rotating.
Loose/worn Head-stock bearings, once loaded up under braking, couldn't vibrate or knock.

As your brakes are all in good condition, I suspect the wheel bearings will turn out to be the culprit(s).

Good luck.

Put the bike on a front paddock stand that lifts the bike in the... ehm, my English, the Place where the forks are attatched to the frame and clipons. Then grab the wheel at 12 and 6 oclock and rock it and check for play.

An update.....

After replacing both front wheel bearings, it seems as the problem has finally been fixed.

The bike has been tested in various conditions, from cold braking tests to heated braking tests .

Emergency stops too.

One of the bearings does not have a smooth feel when you spin it with your finger. I imagine this gets A LOT worse under load.

It still though, has a veeeeeeeeery slight feel, but i think that it will be gone when i get my headstock bearings re-tightened.

Thank you all for your help

igoe1975 wrote:hello, I was getting a knocking sensation from my front end under hard braking and also it felt unsettled ! had the head bearings replaced but its still doing it ?? any ideas ? just had new fork seals also and fresh oil , its a 1989 nc30 . Also to top off my misery now the bike wont start unless you bump it ! when I press the starter button I just get a single click from relay !!! can anyone help ?

head bearings hadn't bedded in and needed adjustment ! and a new starter solenoid ! sorted !!

Glad you got it sorted out, now go out and enjoy!