Front fork oil seal. 97-2641- BSA starfire

[Dunc]

Dear all,
After 40 years living in the back of my garage i decided that on retirement i would turn my attention to my old BSA starfire
The front forks are 6 3/4" centered forks. It has a Twin leading shoe brake. The forks are shutle valve forks.
I striped the forks down since they showed signs of pitting so new stanchions were the order of the day.
I removed the fork oil seals from the chrome holders. Ordered new ones with the part number 97-2641. ( alternative number 29-5313 or 65-5451)
However the newly arrived fork oil seals , being the same diameter as the old ones , are made from hardened rubber/plastic whereas the old seals were more rubbery and hence when i attempt to put the new seals in then because they are hard then it seems unlikely that they will go into the slot provided within the fork seal holder.
I see that there is a special bsa service tool but again even having that will not assist because of the hardness of the new seals.
I just wonder if this has happened to others? If so is there a solution?
I have searched the spare part providers and they all seem to have these hard plastic shell oil seals whereas what i think i need are fork oil seals that are made out of more rubbery material ( like the old ones)and have some give in them to allow them to be pushed into the holder in the first instance and then into the slot in the holder. The workshop manual seems to suggest that the seals are installed from the bottom end(threaded) of the chrome fork oil seal holders.
I hope that this explains the situation and any help would be appreciated in how to get new seals into the holders.
Thanks
Dunc

[Spaceman]

It might be worth measuring the OD of the seals and comparing them with the ID of the seal holder to see what the difference and level of interference is. The manual recommends coating the outside of the seal with a good jointing compound and then using the correct size drift or the special tool. I vaguely remember having a similar problem with a fork oil seal and may well have taken some emery paper to slightly reduce its OD. If it is too tight a fit then it could easily be damaged given that the contact area on the lower side of the seal is not that great.

[Dunc]

Dear Spaceman,
Thanks for the reply. Yes the manual advises jointing compound. One old seal came out easily since there is a slot built into the holder to allow you to get at the back of the seal but the other one was cemented in.
The problem being is the new seal is hard plastic and no amount judicial use of emery paper will get you close to even getting the new seal past the treads of the bottom of the holder.
From looking at it then it seems as if I need some rubbery seals rather then the hard plastic/rubber ones that I have had supplied. But like all these things then maybe I am looking at it from the wrong perspective?  And there is a simple answer out there?
Thanks for your help
Dunc

[Spaceman]

Are you able to measure the outside diameter of the seal and the inside diameter of the seal holder. The inside diameter will be the same for both the threaded part and the un-threaded part. The issue will not be that the seal is made from hard plastic but that its outside diameter is wrong which the measurements should confirm.

[Spaceman]

I have measured up a seal holder which is probably off a B44 but is the same as on the earlier B25's. The seal holder ID appears to be about 1.85". I have also looked at one of the seals being advertised for the B25, B44 etc which is clearly imperial in size and the code displayed shows it has an outer diameter of 1.83".

As said, it would be interesting to know what the outside diameter is of the seals bought for this B25 and whether they have any code lettering on them so that their dimensions can be looked up.

[Dunc]

Dear Spaceman
Thanks for taking the measurements and looking at the seal sizes.
I did measure the internal diameter of the seal holder and came up with the figure of 1.93
I measured the seal and it was 1.88".
On the seal it states it's a pioneer Weston nitrile seal with the numbers 18312537R23/50. I did try and track this seal down to find it's dimensions but I hit a dead end on pioneer Weston website.
As I say because the seal holders have internal lips ( 2 lips one upper and one lower) is where the seal needs to be located then it makes it hard to get the nitrile seal in because it's so stiff. Whereas the old seals that I dug out were rubbery enough that I could flex them enough and extract them from the slot they sat in.
Thanks again for your help. Much appreciated.
Dunc

[Spaceman]

Your seal code shows it has an OD of 1.83", an ID of 1.25" and a depth of 0.37". The seal type is R23 which is rubber covered.

The seal holder I have is basically a round tube of 1.85" diameter but with a single internal internal wall for the springs to bear against on one side and to retain the seal on the lower side. I am assuming your Starfire is pre-1969 because the seal holder changed in that year. From 1969, the seal was in the top of the seal holder and there was also an oil ring in the lower part.

If you Starfire is an earlier one, it would be useful to see a sketch or pics of what it looks like internally?

[Dunc]

Dear Spaceman,
Thanks again.
I have tried to attach a picture but i am told that the file size limit is breached.
My seal holder is tapered .2" at the top and 1 5/8 at the bottom.
I think that these are later forks since it has a tls brake hence 1/4" wider forks.
Being new to the forum then I am still feeling my way around the systems and I will need to try and figure out if it is possible to take a picture that does not breach the 1024 limit.
Like many things in the past its difficult to know the history of who did what and when and 50 years later then it becomes even more of a puzzle.
My next thought was to send it to a someone who probably knows what they are looking at and pay them to locate and fit the correct seals since I feel like I am floundering around in the dark.
Thanks
Dunc

[Spaceman]

I think you have bought the seal for an earlier set of forks. The seal is different for the later ones and is inserted from the top.As said, it also needs an O-ring in the bottom part.

If you go to the BSA unit singles web site you can download the parts books
and see exactly what you need.

[Dunc]

Dear Spaceman,
Thanks.
I buy parts from Dragonfly and they have parts list for b25. That is the reason I bought the "rubber" looking  seal which is listed as 65-5451  67 -68 and the other seal listed for 1969 -70 part number 75-5099 . The 75-5099 seal has the internal rubber seal encased in metal hence I was of the view that the 75-5099 seal would not be able to get  over either of the internal lips.
Hence I am struggling to find a solution
Cheers
Dunc

[Dunc]

Dear Spaceman,
I compressed a picture so hopefully it will be under the 1024 limit.
Let's hope a picture speaks 1000 words.
The old seal on the left.
Hope this helps
Dunc

[Spaceman]

This is the later seal holder. The seal is pressed in from the top end. I assume the lip is far enough inside to leave room for it to fit. Any chance of a pic looking into the top of the seal holder?

[Dunc]

Dear Spaceman,

Thanks for confirming that it's a later type of holder and that the way in  with the seal is from the top.

I hope the picture from the top shows the internal rims which locate the holder.
I suppose the question is would you know what would be the correct seal for this type of later holder? As I have said before the old seals were rubbery throughout and hence they can be easily taken in and out either from the top or bottom.
Hth explain the situation further.
Dunc

[Spaceman]

The correct seal is 75-5099 - it is about 1 mm greater in diameter than the seal for the earlier forks. In the parts diagram, the seal is item #14 but you also need the O-ring, item #16 (75-5199)

[Dunc]

Dear Spaceman 
Thanks again.
I have attached a picture from feked of the 75-5099 fork oil seals. I see that they have the rubber fork seal encased within a metal outer section.
You say that they are 1mm larger in diameter however if it is the case that they are metal clad then I struggle to see how they will go in over the upper inner rim. Maybe you can instruct me as to how to install?
I have dug out the old rubber o rings and I already have new ones which I will slip in once I get the fork seals sorted out.
Thanks again
Dunc