The BSA A7-A10 Forum

Technical => Frame => Topic started by: BigJim on 22.08. 2019 21:55

Title: Progressive fork springs
Post by: BigJim on 22.08. 2019 21:55
Any advice/abuse appreciated.
Have fitted progressive springs as supplied by Paul Goff. Needed to buy new oil seal holders as my existing were too small internal diameter for the new springs. Sadly i went for the stainless which failed to clamp the oil seal, too long on the lower thread! Rather than cut them (and ruin the thread) i used a spare wire spring clamp thingy (that which holds the top fork bush in the slider) as a spacer on top of each oil seal. All now reassembled and pulled up as high as possible into the top yoke.
The problem is the front is still very clattery. Seemingly this is in part/ mostly coming from the chrome shroud that sits on top of the springs and clashes on the bottom yoke
My question is this, rather than smash everything up with a hammer, is there a spacer that can be fitted on top of these shrouds to increase tension in the spring and cut down on the clatter?
Will prob be stripping and rebuilding with original bits tom eve.
Title: Re: Progressive fork springs
Post by: RogerSB on 22.08. 2019 22:12
Hi Jamie, Here's a topic outlining my recent fork overhaul experience ( note the problem with repro oil seal holders).

I don't understand the bit about chrome shroud that sits on top of the springs. My bike is 1960 G/Flash so has the 'trousers', so it may be different than your bike.
Title: Re: Progressive fork springs
Post by: BigJim on 22.08. 2019 23:01
My bitsa is a mongrel of many years. The little shrouds allow the use of gaiters. This does allow relatively simple reassembly at least. The forks are exposed between the yokes.
Will go and read your link and thank you.
Title: Re: Progressive fork springs
Post by: BigJim on 22.08. 2019 23:18
Just reread your posts and wondering if the widget would be a suitable spacer for new oil seal holders.
 *conf2* *bright idea*
Title: Re: Progressive fork springs
Post by: berger on 23.08. 2019 00:31
big jim I am sure you will stop your rattle,-- no pun intended, I remember roger posting about his solution. maybe  you could call at the off license and get many cans with widgets attached *beer* *beer*
Title: Re: Progressive fork springs
Post by: RogerSB on 23.08. 2019 06:25
Jamie, For me the widgets worked a treat. It simply occupies the gap between oil seal and top of bush, if a good fit it will keep the bush firmly down on its seat in the fork leg while at the same time prevents (especially a badly fitting) oil seal from being displaced in the holder by the up and down movement of the stanchion.  My main reason initially for trying them (and thanks to Julian mentioning it in reply 10) was to dispense with the 'awkward to fit' circlips who's only job was to keep the bush down on it's seat.  I bought mine from Feked but unfortunately they were not a very good fit without time spent filing. Whether these from Dragonfly will be a better fit  *dunno*:-

I'm not familiar with gaiter set up, so of no help to you there, but I'm sure others here will come to the rescue.
Title: Re: Progressive fork springs
Post by: Swarfcut on 23.08. 2019 07:46
Jim, This clatter is a bit of a strange one. Reading your first post  I thought you had conventional shrouds, with or without headlamp ears. These are firmly tied to the lower yoke by the pinch bolts and there is usually enough slack in the mounting hole to lift them up against the  top yoke before a final tighten. So there should be no movement here.

 Then  it turns out you have gaiters and exposed stanchions between the yokes. Some folks simply cut away the shroud above the mounting holes, but again the remains of the shroud are tightened against the lower yoke by the pinch bolt. Again there should be no movement or rattle.
  A further possibility is the top of the spring is covered by a shroud similar to a plunger rear suspension spring cup or S/A damper spring cover. This should be clamped against bottom of the lower yoke by the spring exerting pressure between the fork slider and the yoke, a gap here, with the bike on the stand, means the springs are too short for the legs. Too short a spring means the ride height is lower and suspension movement from rest (off the stand) is also less, with a tendency to bottom. Reading the post mentions a spacer, but in use even a short spring will be under tension to carry the weight of the bike, so no shroud movement. but the suspension will bottom easily.  Sounds like legs and springs don't match.  Top fork bush movement is detailed in Roger's post on setting up his forks. Homespun spacers made from a crudely cut length of steel tube were what we used to restore ride height to tired, shortened springs.

 My thoughts are to compare the spring length with published specs and the old springs, and also check the forks contain the correct amount of oil....too little and they will clang and bang as the the bottom of the leg hits the bottom of the slider, without the hydraulic cushion. I do not think the problem is the shroud itself, more a too short spring hitting the shroud after a large suspension rebound. A picture  of the set up would help.

 You would think simply changing the springs would not require new oilseal holders....If the spring diameter was wrong, what chance of other manufacturing errors?

Title: Re: Progressive fork springs
Post by: BigJim on 23.08. 2019 17:32
Am now convinced these springs are too short. Wonder if anyone else has had this problem with Paul Goff springs? I will prob go out and refit original springs and oil seal holders tonight but have had a long week at work and have 2 cans of Guinness in the fridge and it's a friday! Hoping to get the front end performing well as i would like to take the A10 to Spain in Sept.
Thank you for support offered, am struggling with expensive parts that seem to not fit 50% of the time. Hey ho , trying to count my blessings.
Title: Re: Progressive fork springs
Post by: Swarfcut on 23.08. 2019 18:15
Jim, Drags have a list of standard springs, length, wire gauge, number of turns etc. B40 springs are very similar , but a bit shorter...I am sure Mr G will be amenable if a rogue set has crept in, so do your researches.

 Easy to swap out, all the bits have recently been apart and no doubt all the tools are readily to hand, so just leave the new oilseal holders on and finish with a Guinness.


Title: Re: Progressive fork springs
Post by: JulianS on 23.08. 2019 18:21
Parts bulletin below gives spring lengths.

The 89 spring was used on all the late solo A10s.

Measuring the spring and seal holder in my parts box;

Spring diameter 47mm approx.

Seal holder bore 49mm approx.
Title: Re: Progressive fork springs
Post by: coater87 on 23.08. 2019 21:58
 I had a bad rattle also, because a PO had relieved the top edge of the circlip groove probably attempting to make installing easier. This meant the circlip could pop out and it did!
 I also took Julians great advice and installed widgets. They work excellent,  I am in America so NOS is cheaper than poorly made reproductions.
 I had to shim my fork seals .060, so i used plastic shim sheet you can cut yourself. I believe a layer of orange and yellow did the trick.
 My forks no longer rattle or leak!

Title: Re: Progressive fork springs
Post by: Jules on 01.10. 2019 03:21
hi Lee, what did you do to stop the weepage past the threads? cheers
Title: Re: Progressive fork springs
Post by: coater87 on 11.10. 2019 03:25
 Sorry I did not see this.

 I used one layer of thread tape, than at the bottom where BSA used twine i twisted the thread tape into a rope shape.

 I think if the top of the legs above the threads is clean and flat, and the seal is pressed down squarely with a little pressure, that goes a long way to making them leak free.