Fork Damper - Need advice + pictures

My problem - front forks - clunk sound on rebound over a bump. (No it is not head bearing - checked that).

My thoughts - damper not working correctly - especially on rebound.

Have rebuilt forks with bushes and seals. (Yes oil levels are correct & I've done this a couple of times before so it is not new to me.)

Now investigating the damper - because I never took it apart during rebuild.

I have series 2 (1989 - 1990 - 1991??). Damper is part 51430-MS2-003 DAMPER, FR. - pictures below.

I note that the damper on the series 3 (1993 - 1996???) is a different part and also has a rebound damper spring in addition. Damper is part 51430-MZ2-003 DAMPER, FR. pictures below of actual Series 3 damper but I cant find picture on inside of Series 2.

QUESTION & ADVICE + MY NEEDS.
Anyone had this problem with this bike? Advice please.
Anyone taken the series 2 damper apart? Picture of inside?

If I have pictures before I take it apart I'll have a better plan of attack.

Thanks in advance....

 

Hey Naga,

I rebuilt a set of Mk 2 forks earlier this year, but unfortunately didn't take pictures of the process.

It is straightforward - and easiest if you have access to a rattle gun for getting the bottom forkleg allen bolt out. Then just disassemble, clean, measure and reassemble. As you know oil levels are critical, so I just accurately measured the correct amount and tipped it in - measuring from the top as a secondary check.

Cheers, SB

 

Thanks for the quick reply SB but appears I didn't put my post clear enough.

I've rebuilt the forks several times before and never had an issue with that process. What I've not done, and am in need of advice (pictures of), is the rebuilding of the damper.

QUESTION & ADVICE + MY NEEDS.
1. Anyone had this problem with this bike? Advice please.
2. Anyone taken the series 2 damper apart, exposing the damper rod, rebound spring, piston ring and bottom piece? Picture of inside?

If I have pictures of the damper rod, rebound spring, piston ring and bottom piece before I take it apart I'll have a better plan of attack.

Thanks for your post SB... hope this makes my needs clearer.

 

Were the springs inadvertently put the wrong way, easily done, as the tighter coils should be at the base as I understand.

 

Thanks for your thoughts Bullroarer. Much appreciated.

Reality was that also the original springs were put back in the same way they came out, as per the w/shop manual. Additionally the main springs have little/no effect on rebound damping which appears to be my problem.

You might like to read the attached about progressive springs which includes
" Mechanically, it makes no difference which way the springs are installed. Some manuals will state; install the spring with the close wound end towards the bottom.
This is done because sometimes there will be less spring noise.
The springs will perform exactly the same regardless of which direction they
are placed."

http://www.progressivesuspension.com...rings/3055.pdf

HELP NEEDED - STILL LOOKING FOR - PHOTOS / PICTURES OF - series 2 damper, exposing the damper rod, rebound spring, piston ring and bottom piece.

 

Just another thought. You know that the replacement rings, 2 for each side, and each of the rings are a different width. Well its these rings have a split in them, are the splits in line with each other, as that may reduce their effectiveness, as the fluid has an easy path, if say one of the splits was at the 12 oclock position as looking from above and the other ring was at the 6oclock position, then the path of the oil is therefore interupted, ie better compression, a bit like piston rings on an engine, that may be issue....perhaps....maybe ?
Oil grade perhaps, Im using ATF.
Having rebuilt my forks recently I have yet to try them , but they seem to have good compression. Presumably you pumped the damper up and down to get the oil through before you screwed the top allen cap in....again, I'm not doubting your skills, but even I can for get to do a vital thing sometimes. Mike.

 

Hey Mike - Many thanks for persevering with me on this because now I think we are getting to the nub of my problem...

You will recall that I'm investigating the damper. because I've never taken it apart during rebuild, I don't know exactly what is inside. In my research (parts on line and workshop manual) they don't show or talk about the internals of the damper.

Now you talk of ..
"replacement rings, 2 for each side, and each of the rings are a different width. Well its these rings have a split in them, are the splits in line with each other, as that may reduce their effectiveness, as the fluid has an easy path, if say one of the splits was at the 12 oclock position as looking from above and the other ring was at the 6oclock position, then the path of the oil is therefore interupted, ie better compression, a bit like piston rings on an engine, that may be issue."

This all sounds very logical to me but I've never seen these rings. Do you have any pictures of them? What are they made of? Do you know what is a part number for them or where they can be purchased? I'd like to purchase these rings before pulling the forks out and apart again.

The other thoughts you raised .. Yes I used fork oil 10W, correctly measured, and pumped out the air before fitting top cap. I've replaced seals and bushes on this bike 3 times before and never had this rebound problem after reassembling.

Once again Mike, I really appreciate your insights and thanks in advance as I'm obviously missing something.

=================================

 

Hey Naga,Try Honda CBR1000F Parts & Accessories - Parts N More - Japanese Vintage Motorcycle Parts[fitting]=custom



Scroll down to Fork DU Bushing set.


I must admit I'm a little confused here. Are you saying you have not previously pulled the internals out of the forks apart from the main spring?


When are you likely to do this, because I'm back from France in a few weeks and will probably be heading to Melbourne to visit a mate shortly after my return and would be more than happy to help. I've rebuilt the dampers on many bikes Naga.


Cheers, SB

 

Hi Seb - Thanks for the follow up.

Over the last 25 years I've rebuilt these forks 3 times ( seals and bushes top and bottom) with out problem. On doing this I have removed the damper (Damper is part 51430-MS2-003 DAMPER, FR.) but never taken the damper apart into its component pieces (it is sold as a complete unit and not itemized as parts as far as I can ascertain). It is the internals of this damper that I'm in need of the details of.

Your link is just referring to the standard fork bushes - nothing to do with the damper.

Hope you enjoying France & if you are coming back by Melb let me shout you lunch and come see the new VF750F I've restored over winter. I started with 20 boxes of parts as here ...

 

Ok, thanks Naga, now I understand.

Have a look at this - I found it good to understand the basics of fork damping and is very similar to the CBR1000F 1989-1992.

Damping Rod Forks

If I'm heading to Melbourne I'll email you and take you up on your offer - I'd love to see the VF750F

Cheers, SB