Forks knocking at full extension/rebound

[warren3200gt]

Before I strip both legs again anyone got an idea what would cause the forks to knock, or over extend causing a knock, when I go over an uneven surface. Compression is fine. So trying to get my head around what to look for. Forks are z1b

[Pigford]

Double check your engine mounts (front especially) are tight

I had similar situation which I thought was the forks...….. but turned out to be loose front engine bolt knocking.

[warren3200gt]

Nice lateral thinking but I dont think thats it as it had a4 forks on previously and they were fine., but easy enough to check so I will thanks.

[Al]

It could be the order of assembly. J forks (similar) are very easy to get the 'top out spring' in the wrong place and have it mashed to bits by the bottom of the fork inner stantion.
AL

[marmck]

Does your steering head need adjusting ?

[warren3200gt]

Does your steering head need adjusting ?

No not head adjustment. Im sure its something to do with the fork internals, like an air lock or the return valves not operating as they should. Could be not enough oil but they have 170ml as per the service manual but that doesn't sound like a lot?

[warren3200gt]

It could be the order of assembly. J forks (similar) are very easy to get the 'top out spring' in the wrong place and have it mashed to bits by the bottom of the fork inner stantion.
AL

Assemble as per the parts list diagram. Guess Im just going to have to strip them again but unless I find something obvious I did then I know I'll re assemble them exactly as I did first time.

[ADRIAN H]

It could be the order of assembly. J forks (similar) are very easy to get the 'top out spring' in the wrong place and have it mashed to bits by the bottom of the fork inner stantion.
AL

Assemble as per the parts list diagram. Guess Im just going to have to strip them again but unless I find something obvious I did then I know I'll re assemble them exactly as I did first time.

Strip them and post a picture.

[warren3200gt]

Yep, will do. Not going to get to until later in the week though the missus has decided the hall needs redecorating, no sense of priorities these women.

[warren3200gt]

Quick thought, is it better to fill the oil with the forks fully compressed, ie wheel on the ground or fully extended ie wheel off the ground. Or does it not matter? Thinking about expelling any trapped air?

[Julian_Boolean]

Quick thought, is it better to fill the oil with the forks fully compressed, ie wheel on the ground or fully extended ie wheel off the ground. Or does it not matter? Thinking about expelling any trapped air?

It doesn't matter, any trapped air will make it's way to the top pretty quickly.

As for the knocking, worn bushes, loose damper rod or misassembly, but it could just be something loose.

[warren3200gt]

Got the forks disassembled and now a bit confused! The first pic is of complete fork parts. The second of the damper ass that was in them. They look very lightweight for a 900. So don't think they are the correct ones.
Had a route in the parts bin and came up with some that look much more like the correct bits, the third pic. Question is, are they? and there is a red collar missing from one of them. What is that supposed to do and is it necessary? I can guess the answer and where can I get one or would one turned from nylon suffice? Having had a close look at the pic on the same assembly there appears to be a seat washer missing for the little weak spring also.

[warren3200gt]

That seems to have sorted it. Made the missing bits and fitted the ones in pic three. Front end is a lot stiffer which I like and no knocks anymore. Happy days although begs the question what are the original one from?

[Philippe]

Hi Warren
if they're aluminium they could be from a Z1 front fork, if i'm correct those aluminium tubes were replaced with steel tubing from the Z1a onwards.
GrtZ
Philippe

[warren3200gt]

Ok thanks Philippe. No good to me, anyone need them for a Z1?