Knocking forks

[Ian DB]

My new (to me) CB500 K2 forks knock when you rock the bike backwards and forwards as if the forks are extending to their maximum and the damper rod is  hitting the top of the damper? I have stripped the forks, replaced the seals, refilled them with the correct amount of oil and added 10mm spacers between the top of the springs and damper rod lock nut, just for a bit of added preload as they seemed a little soft, and it still hasn't cured it. All in all the forks appeared to be ok when I had them stripped down.

Also I have noticed that when you rock the bike with the brake held slightly on, there as an amount of knocked that comes from what appears to be the free play in the pads/calipers. The pads are new and although the previous owner didn't smear the sides and back of the pads with silicone grease, I have now done this and also added shims on the top and bottom of the caliper pivot pin to remove any up and down play, the knocking still remains but is only slightly improved.

Having only ridden modern bikes until this getting this one its seems a bit strange.

Cheers
Ian

[WPF81S]

I suspect you need to adjust the headstock bearings. Regards Iain

[Ian DB]

Hi Iain

I did that while the front end was stripped down, athough I have retained the original ball bearing arrangement for now as they also appeared to be in good conditon

Ian

[Green1]

Hi Ian I had the same thing with my 750 sounds like your forks are in slightly twisted.Slacken everything don't forget the front mudguard and spindle.Do up the top yoke and then rock the bike back and forth with the front brake on and then do everything up again.

Mick 

[Ian DB]

Hi Mick, Thanks for that, will give it a go and see how we get on.

Cheers

Ian

[mick]

Hi Ian let us know how you get on  mines doing it on one fork leg think i'll give it a go to  cheers Mick.

[Ian DB]

Had a go this morning and no difference, easiest way to see whats actually happening is to pull back on the bars while its on the stand and the forks extend to their max and knock as I assume the damper rod is still hitting the top of the damper although its so hard to pin point where the clunk comes from.

There is no tension on the forks when the bike is on the stand and its easy to remove to top cap without fear of it shooting out of the fork tube.

Could it be that the damper and/or springs are shot? and would ATF oil instead of the 10-30's fork oil i've used?

There is no real knocking when rocking the bike backwards and forward so long as you hold the brake on hard. still knocks with the brake on slightly. This might settle down as the pads settle in?
 
Ian

[Green1]

O yeah you just reminded me I changed my springs as they were about 10mm shorter then the min recommended length and that was what sorted it on the 750.Sorry I wasted your last half hour The top cap is now a pig to put in and it takes your eye out now when it's undone
It was my Triumph that was knocking because they were twisted.I seem to have a memory of a goldfish lately 

[Ian DB]

No worries Mick, it was worth a try anyway. The springs are well within tolerance, but must be tired. Will look for replacements in due course.

Ian

[bomber]

Any luck with the forks? Have you fixed it?
Mine where knocking on braking, it started after I took spacers out, think new springs are needed.
 

[Ian DB]

Hi Bomber, only just read your message, they are still the same, they only knock when rocking the bike backwards and forwards, its the damper rod hitting the top of the damper, which only happens when putting the bike on the centre stand and you then pull back on the bars thus extending the forks to their max. No issue on the road. Have now also got a complete set of spare forks which when i get round to overalling them will see if these do the same, my guess is its normal.

Cheers

Ian

[Rob.b (Rob Birkett - RIP)]

Hi.
Mine does exactly the same knock when the forks fully extend.

I would like to make it stop.

Rob

[Bryanj]

Sorry to upset you but a knock on "topping" is normal as it ain't supposed to happen that you lift the forks all the way up

[Rob.b (Rob Birkett - RIP)]

Ah, interesting, and when I think about it I probably haven't owned a motorcycle with a mainstand other than the Honda for 30 years, so I will never have had the opportunity to bounce forks on any other bike than the Honda, which that probably explains why I have never felt the knock before.
 I suppose the way to stop it knocking is to stop bouncing it on the main stand.

Cheers for the post. Rob

[Seabeowner]

Old subject. But just getting my 500K1 ready for its first MOT in 10 years. I have the clunky forks when putting the bike on the c/s. I had one of these back in 1974 and I don't ever remember the clunk. But I had just come from 3 years of Triumphs so maybe anything was an improvement.
Is it the damper rod clunking against its endstop when extended and has anyone had an issue at MOT? Testers don't like clunks, but as already said on the c/s is not real world.
thanks