Author Topic: Fork Overhaul  (Read 973 times)

Offline RogerSB

  • 1960 Golden Flash, Plymouth, Devon, England
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Fork Overhaul
« on: 27.05. 2019 16:17 »
Hi everyone,

Yesterday evening I started my forks overhaul. Things went fairly easily until I tried to remove the first oil seal holder, no way, tried & tried, applied a little heat from hot air gun, strap wrench, but eventually I had to carefully (without damaging the thread) take a hack saw to it (see photo). The problem was that someone in the past had completely destroyed the internal slots so the removal tool just rode up two nice ramps and slid around. Also they were stuck with some type of thread locking compound.  Happily the other holder was ok and I managed to unscrew that one fairly easily with the tool. So new oil seal holders  *sad2*.

As I suspected the springs definitely need replacing, they’re either poor repro or very tired. They look ok, clean and without any sign of rust but one measures 10 1/2” the other 10 5/8”. However, although I thought I may have to replace the stanchions and bushes they seem ok (well, to me they do).  There isn’t any scoring and both top bushes slide up and down the stanchions smoothly with no detectable play. There’s is a polished shiny patch, just above the oil holes, on both stanchions and on one there is a mark running part way around the circumference, which I can just detect when I run a finger tip over it but it’s not cracked or pitted. I imagine it was the start of some corrosion at sometime in the past when the bike was laid up or standing idle for a length of time, but luckily caught and arrested in time. It can be seen near the bottom bush in photo no 2.

I’m fairly competent and happy to take things apart and put back together again, having spent a lifetime doing it, but I’ve not got any engineering facilities (but I have got a M&W vernier gauge  *smile*) nor am I a trained mechanic or engineer.  I know it’s difficult to judge from photos, but any comments, confirmation (or not) of my observations would, as always, be welcome.

Roger.

1960 Golden Flash

Offline Swarfcut

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Re: Fork Overhaul
« Reply #1 on: 27.05. 2019 18:43 »
Some of the best I've seen, usually they are well pitted and gouged.  Light scoring is of no real consequence, and if the seals did not leak before, I would use the legs with no worries.

 Check for bowed legs by rolling on a flat surface, wash the sliders out, and test fit the new oil seal holders on the sliders first..no fun struggling to get the threads to mate after you have got the top bush circlip  in place and they don't fit. Take care with the threads, they cross easily, and a smear of silicone or hylomar  will seal  them and retain any weeping oil within the holder.

  Use the bottom yoke pinch bolt as a clamp to hold the leg still when you tighten the bottom bush nut. 

 Swarfy.


Offline RogerSB

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Re: Fork Overhaul
« Reply #2 on: 27.05. 2019 20:34 »
Some of the best I've seen, usually they are well pitted and gouged.  Light scoring is of no real consequence, and if the seals did not leak before, I would use the legs with no worries.

 Check for bowed legs by rolling on a flat surface, wash the sliders out, and test fit the new oil seal holders on the sliders first..no fun struggling to get the threads to mate after you have got the top bush circlip  in place and they don't fit. Take care with the threads, they cross easily.

  Use the bottom yoke to hold the leg still when you tighten the bottom bush nut. 

 Swarfy.

Thanks Swarfy, that's encouraging and, as always, you come up with some good advice, like temporarily clamping the stanchions in the yoke to tighten the nut (I never thought of that to undo) and I used my vice with an old towel around them. Luckily both nuts unscrewed easily. Yep! I'm going to be careful buying the oil seal holders as I've heard some don't have the slots inside to be able to use the tool.

I've stripped and rebuilt a few Brit bikes in the past - but that was many years ago and details get forgotten. Here's photos of a D1 Bantam I restored in the 80s and used as my everyday commuter transport to and fro the city of Plymouth. I was light and great for that, especially in the ice and snow. The young lad in the photo is my son (now nearly 50  *eek* ). Parked in the background is my dark green 1950 Austin Devon and pale blue 1963 Morris 1000. Both cars were restored by me. The Austin Devon was used in one of the Miss Marples series.

1960 Golden Flash

Online KiwiGF

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Re: Fork Overhaul
« Reply #3 on: 27.05. 2019 21:47 »
I bought some seal holders from dragonfly and they had different diameter slots for the tool to the oem ones, so the standard tool would not work anyway, I’ve since read this is not unusual.

A patch of chrome fell off within a year so I’d buy stainless next time.

I use ptfe plumbing tape twisted to form a piece of string (I think bsa might have used string or hemp) to act as a seal at the very bottom of the seal holder thread. I don’t wrap it around the actual thread in true plumbing style, i don’t  use any sealant glue, this is so the next owner will not struggle to get the holders off   *eek* in my limited experience oil leaks at the thread are not common and probably mean something else is not right.
New Zealand

Last had an A10 in 1976, in 2011 it was time for my 2nd one.

1956 Flash Frame EA7-168x Eng. CA10 913x, left BSA together for Liverpool, 5th Dec 1955.

B31 “hot rod” (yeah right)

Armstrong Siddeley Whitley for rainy days (with wife).

GL1800 Goldwing not sure why yet

Online Angus

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Re: Fork Overhaul
« Reply #4 on: 28.05. 2019 09:58 »
I have not used them yet but got a stainless set of oil seal holders from Barleycorn, they look really good, the price was right, Simon is helpful and was local. The old ones still look OK and I could not get them off and did not want to cut still good holders, so the new ones are in a box awaiting the demise of the old ones.
1961 A7 since 1976
1960 A10 Gold Flash Super Profile Bike
1958 Matchless G80 Project
1952 Norton Model 7 Plunger (becoming a project)

Online RDfella

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Re: Fork Overhaul
« Reply #5 on: 28.05. 2019 11:09 »
I've had BSA's (A7, B31, GS, M21 etc for over 50 yrs and rebuilt many of their forks without problems. Until my GF. New S/S holders (because I was getting tired of replacing rusting chrome ones on my other bikes) and one leaks at the thread, even with PTFE. Problem sorted now - it no longer leaks because it's run out of oil. Frankly, after all the hassle I've had with that bike I can't be bothered to fix it. After the oil problem I put it at the back of the shed and there it stays. But to the issue of fork seal holders - as I said, I can't be bothered to look into the leak on the GF, but if I did I was wondering whether the recess for the seal could be too deep, meaning the thread bottoms out before the seal is compressed against the fork slider. Anyone experienced this?
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline Swarfcut

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Re: Fork Overhaul
« Reply #6 on: 28.05. 2019 11:49 »
   Funny that you mentioned that RD. I realised that checking the relative depths of the slider and holder threads on my forks, only the friction of the seal in the holder kept it in place, and with the leg moving like a fiddler's elbow (a less crude expression of the old in out), there was a good chance the seal  would dislodge and move up and down. I made thick section thin wall aluminium washer which supported the seal on the deflection stroke.

 Took a bit of experimentation to get the thickness right to support the seal gently, while allowing the holder to screw fully home  so that the washer was clamped between the bottom face of the seal and the top of the slider. I thought it an improvement, and for all I know the seal moving could be the reason they weep on  many bikes. Touch wood, no leaks.

 Swarfy.

Offline RogerSB

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Re: Fork Overhaul
« Reply #7 on: 28.05. 2019 13:05 »
Done a trial fit of the top bushes this morning to know what shim sizes I need to get.  I used a pair long nose locking pliers with a cable tie to protect the threads and clamped the end of the circlip in place, then worked around pushing it down into the grove. Took about 30 seconds for each fork leg. But that was after spending an hour late last night trying to do it with just a screwdriver. Lost the clip several times when it shot off like a bullet and I must have spent half the time looking for it amongst the other stuff in my garage. Hope it's as easy with the stanchions etc in place.

Regarding oil seal holders: I was planing to buy stainless steel ones but the supplier I want to use is out of stock at the moment. That's Monty's Classic Motorcycle Workshop in Cornwall. Monty is also a former marine so I like to support him when possible. Also at the same time I want to buy fork springs, a rear sprocket, sprocket bearings and a few other bits and I can drive there and see what I'm buying. He has chrome ones in stock, which are made by LF Harris, in Torquay (who started building Triumph Motorcycles again in the early 80s after Meriden closed), so they should be high quality.

I have a pair of NOS Halls NA181 oil seals with metal bodies that I'm going to use. Could it be the new all plastic ones that are now generally available that are not deep enough and causing problems?

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Re: Fork Overhaul
« Reply #8 on: 28.05. 2019 16:23 »
Swarfy – glad to see someone else thinks along the same lines. From an engineering point of view, shouldn’t the holder clamp the seal before bottoming out on the thread? That’s what I intend doing in future.
And as for shimming the top bush – that’s another ‘director’s girlfriend’ design. The way it’s made you can’t get it tight because if you took up all the slack the circlip wouldn’t go in. For the design to work the circlip would either need to be a flat one, or located at far less than half its wire thickness. In the latter case the bush could easily push the circlip out. Wonderful.
 *pull hair out*
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline Swarfcut

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Re: Fork Overhaul
« Reply #9 on: 28.05. 2019 17:55 »
  RD.   Yes, but the seal would be clamped slightly in compression as the holder bottoms against the slider shoulder. Otherwise you will get a gap between shoulder and holder. Closing this gap will squash the seal, so your washer needs to be just thick enough to prevent the seal moving, but still allow the holder to screw down to the slider shoulder.

  I greased everything and put a dab of body filler in the gap between the bottom of the seal and the top of the slider, then tightened down the holder.  The cured filler came out easily because of the grease, and gave me the basic height of the required spacer washer.

 Blame the cost accountants for the wire circlip. A conventional flat internal circlip would do a better job, and be less hassle to service.

 Swarfy

Online JulianS

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Re: Fork Overhaul
« Reply #10 on: 28.05. 2019 19:40 »
The circlips are a pain but you can replace them with the A65 damper rod fork spacer which goes between the top bush and the lower edge of the oil seal. part 68 5134

Offline Swarfcut

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Re: Fork Overhaul
« Reply #11 on: 29.05. 2019 07:22 »
Julian    Once more you brought the Cavalry. Just had a look at Drags parts list for 1966, there it is, described as a Widgett, around £10 each. No wonder they have excellent stock. Fork or seal spacer would be a better description.

 I made my support washers long before the luxury of internet parts searches, but even so never considered an official part like this would ever exist.

 Thanks once more for your attention to detail.

 Swarfy.

Online Greybeard

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Re: Fork Overhaul
« Reply #12 on: 29.05. 2019 09:34 »
This thread is full of useful information and tips! Thanks guys.

Offline RogerSB

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Re: Fork Overhaul
« Reply #13 on: 29.05. 2019 11:14 »
The circlips are a pain but you can replace them with the A65 damper rod fork spacer which goes between the top bush and the lower edge of the oil seal. part 68 5134

As soon as I saw your post Julian I remembered reading about that somewhere  *eek*  but where?  Eventually I remembered - it was on here!  *conf*

https://www.a7a10.net/forum/index.php?topic=10447.msg77762#msg77762

Reply no 7 by jjbsa in 2016.

(Edit) I see feked.com sells them:-
Fork Retaining Ring/Cup - B25, B40, B44, A7, A10, A50, A65 + Triumph TR25W
OEM: 68-5134, 97-2643
£4.25 (add vat + pp).

1960 Golden Flash

Offline RogerSB

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Re: Fork Overhaul
« Reply #14 on: 29.05. 2019 12:28 »
I'm going to give the retaining cups a try. Just ordered 2 from feked and with vat and 2nd class post cost £12.54.

1960 Golden Flash