BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: TIGER on 30 June, 2017, 08:18:10

Title: C15 Forks
Post by: TIGER on 30 June, 2017, 08:18:10
After a few short test runs my forks are leaking badly.
So no chance of an MOT yet.
Have removed forks but seals look new but not a tight fit on stanchions.
In haste ordered 4 seals from Burton bikes but not sure if these will seal.
Stanchions look good no sign of ware.
Could anyone provide the diameter of stanchions please.
OR ANY OTHER HELP
Summer riding time is going fast !
Regards
            Tim
Title: Re: C15 Forks
Post by: JulianS on 30 June, 2017, 12:21:41
I think the forks are 1 1/4 diameter but it is easy enough to measure yours at the upper diameter.


Main thing is to make sure there is no damage/pitting/corrosion  to chew up the seals either in use or when putting the seal holder back on over the upper part of the leg.
Title: Re: C15 Forks
Post by: TIGER on 30 June, 2017, 13:43:13
Yes the diameter is 1 1/4
The space for the seals in the crome holders twice the seal thickness and could allow the seal
to "waddle" in situ. Also there is a machined ridge which will not allow further reduction of the
Seal space.
There is no ware or damage on the stanchions.
Two seals are fitted each side and it appears new seals and possibly stanchions have  been fitted
recently.
The new seals purchased from Burton arrived this morning and seem a Good seal on the stanchions
but not in the chrome holders.
So could leak between outside of the seal and seal holders
Looking at the possibility of packing spacers/and or glue??
Regards
           Tim
Title: Re: C15 Forks
Post by: JulianS on 30 June, 2017, 14:36:04
Seals should be a good fit in the holders.

You could ask BBB about the seals supplied and the fit.

How does the outside diameter of the old ones compare with the new?

(according to my old Paynes seal lists the seal measures 31.7 mm inside diameter x 39.73 mm outside diameter x 3.9 mm deep - yes that is what it says with no Imperial measure given!!)

Depending on how lose the fit you might be able to wrap some PTFE tape around the outside of the seal but honestly you should not need to bodge with the correct parts.
Title: Re: C15 Forks
Post by: TIGER on 30 June, 2017, 16:46:38
Thanks for a quick reply Julian.
All the seals old and new comply to your figures within a very small difference.
The new are a more favorable size that is slightly smaller I/D and slightly larger O/D
My main concern is the deeper recess in the fittings.
By the way which way up are the seals fitted ?
Regards
           Tim
Title: Re: C15 Forks
Post by: JulianS on 01 July, 2017, 10:08:03
Lower seal lip down to keep oil in.

Upper seal could go either way - Rupert Ratio suggests lip up to keep dust out.

Or it could go lip down to assist with keeping oil in.
Title: Re: C15 Forks
Post by: MICKREEVES on 02 July, 2017, 14:58:36
A quick fix so you can ride again. drain all the oil from the forks, carefully clean all traces from the outside.
Put the oil back after MOT.
(You dont get old but you get crafty)
Mick
Title: Re: C15 Forks
Post by: TIGER on 07 July, 2017, 23:31:20
Forks done.
Burton seals are fine after all.
Put additional O- Rings to seal at threaded joint.
No leak yet so fingers crossed.
Still some tuning to do with the 375 carb running on 200 main jet but seems a bit rich so I
have a 180 to test.
Probably need to check timing because starting seems more difficult although once running
Goes well.
Engine is rebuilt so need to run in.
Next step is MOT.
THANKS AGAIN FOR ALL THE HELP
Regards
            Tim
Title: Re: C15 Forks
Post by: SIE7RA on 16 July, 2017, 21:09:45
How much oil have you put in,some workshop manuals give an incorrect figure it should be 1/6 pint in each side
Title: Re: C15 Forks
Post by: TIGER on 17 July, 2017, 05:32:46
100 cc
Title: Re: C15 Forks
Post by: SIE7RA on 20 July, 2017, 20:21:56
100 cc is correct I use Fuchs Silkolene heavy fork oil SAE 20 No problems with this.
Title: Re: C15 Forks
Post by: TIGER on 21 July, 2017, 09:35:05
Thanks for that.
I am using classic 20/50 at the moment.
Tim