The BSA A7-A10 Forum

Technical => Frame => Topic started by: Jes-can on 11.06. 2012 16:49

Title: Top Yoke and Forks Fused!
Post by: Jes-can on 11.06. 2012 16:49
Hi New member here. I did some searching last night before joining the forum, but couldn't find any posts about this.

I have a 1957 A7 which I am restoring. Most of the bike has come apart quite easily, but I started pulling the front end apart last night and when I got to removing the forks i discovered that they appear to be fused to the top yoke. I have the Hanes manual and followed all the steps. Not sure what to do at this point to get them out. Any suggestions would be greatly appreciated. The alternative if they are completely stuck would be to grind the top yoke off and replace the front assembly, but after looking on Ebay, it doesn't seem like these parts are in abundance.

The rest of the bike is in decent shape, but I guess if the forks have not had any attention recently I could see how this would happen.

Thanks in advance for your response.

Jesse
Title: Re: Top Yoke and Forks Fused!
Post by: fido on 11.06. 2012 17:11
Try soaking the area with penetrating fluid and leaving it for a few days. As you will appreciate, the forks are held in the top yoke by a taper so they are tighter than equivalent Japanese forks but they don't usually give much of a struggle to come apart. I don't know what the manual says but when I do them I loosen them at the bottom yoke, loosen the top nuts (bolts?) a few turns, hold a block of wood on the top of a nut and give it a tap with a lump hammer.
Title: Re: Top Yoke and Forks Fused!
Post by: Goldy on 11.06. 2012 17:53
As fido says they can be tight on the taper.Make sure the bottom yoke is free by knocking a wedge into the clamp slot. For the top I use an old fork top nut which I drilled and fitted a 1/2 inch bolt and it gives me something to get a decent strike at with the hammer. Try warming the top yoke to expand it a bit. All the best with it.
Title: Re: Top Yoke and Forks Fused!
Post by: Greybeard on 11.06. 2012 17:56
This link shows the official fork strip down

http://www.bsawiki.com/index.php?title=Chapter11
Title: Re: Top Yoke and Forks Fused!
Post by: Jes-can on 11.06. 2012 20:48
Thank you for the replies. Put the but back in and giving that a few taps sounds like it makes the most sense. I'll give that a go and let you know how I make out.

Cheers,
Jesse
Title: Re: Top Yoke and Forks Fused!
Post by: duTch on 12.06. 2012 00:44
Quote
Put the but back in and givi.....

Not quite sure what that means??

 Hiya Jesse, It may be worth putting the angle grinder on ebay- get rid of the temptation! *smiley4*
 
 Also maybe worth backing off the stem adjuster a touch to allow the bottom yoke to move a tad, in case the bottoms are also tight??

 Also something (like a lump hammer or heavier, or piece of wood/pipe from the floor up) under the top yoke(next to where you're banging on top) will help not bend it, and sometimes a rap on the side of the taper helps.

 Good luck, duTch
Title: Re: Top Yoke and Forks Fused!
Post by: Jes-can on 12.06. 2012 01:17
Sorry hasty typing! Sorry I meant the top nut!

I'll try all these suggestions tonight and see how it goes.
Title: Re: Top Yoke and Forks Fused!
Post by: muskrat on 12.06. 2012 08:50
 G'day Jesse, welcome to the forum.
                                                 Dutch has a point as I have had them that tight in the taper that a good belt may have bent the yoke. Buy yourself a nice new pair of nuts (mine are worn out too  *eek*) so you can give the old ones a good flogging. Screw'em in nearly all the way and hit with a hide mallet, Work your way up the knockometer range till it gives. WHAT, you only have one hammer. LOL.
Cheers
Title: Re: Top Yoke and Forks Fused!
Post by: Topdad on 12.06. 2012 10:49
Hi Jesse, and welcome. All of the above are how I've just stripped my forks down on Sunday and will work. Musky's idea to buy new nuts can sort out another question before you ask it ,how to get them fitted again particularly if you have any sort of headlight cowl on the bike. Well no need for fancy special tools ,use one old nut has advised has the dismantler (keep for future use ) and the other cut/grind the edges so that it fits through the tapered hole ,drill an hole through centre ,buy a length of threaded stud from an hardware shop ,one nut above 2 below , screw into fork leg push the threaded stud up through yokes/cowl and a large socket which you p[lace on the top yoke ,a few washers on top of the socket run down another nut ,pull into taper and pull up fork leg  with a spanner on the nut bingo tightnen bottom yoke pinchbolt , remove "customised tool" ,insert bright and shinny new one bingo jobs agood 'en !! took much longer to write than do ,I promise. Sorry yours is proving awkward but normally it's one of the easier jobs and I'm positive that with a bit of "persuasion" ie big hammer you'll get it done, best wishes BobH.   
Title: Re: Top Yoke and Forks Fused!
Post by: duTch on 12.06. 2012 11:05
Hye Topdad, I'm sure that'll work.......after a couple of reads,.... and, musky reckons I did too much keepin' the battery topped up???...uh..you had to be there..

Cheers,
          duTch
Title: Re: Top Yoke and Forks Fused!
Post by: Jules on 12.06. 2012 11:36
I have always found that a (good!) tap onto the loosened nuts breaks the taper ok, however, I'm interested in Top dads assy. process and whether others have found it necessary to actually use a special tool for reassembling into the taper. I had assumed that just tightening the nuts on the top would pull the taper in and lock up the top into the yoke adequately, is that not true?? cheers
Title: Re: Top Yoke and Forks Fused!
Post by: Topdad on 12.06. 2012 12:17
absolutely right 'cept those canny BSA engineers went and covered the fork legs at the top with a cowl /shroud or headlight ears which those pesky legs have to go through  and sods law dictates that has you push the fork leg upwards so it'll slip back into it's retracted position , bloody infuriating so I've found my method stops hammers and bit's of bike being thrown threw the shed wall ,oh you can use a wooden broom handle too ,through yokes twist into threads and pull gently upwards  but it comes unstuck sometimes and anyway the wife usually wants it back normally just when you need to work on the but always  a standby. By the way it costs about £3 from hardware shops  and you get some extra studding which is always useful,hope this is of help, best wishes BobH
Title: Re: Top Yoke and Forks Fused!
Post by: Greybeard on 12.06. 2012 12:19

.. no need for fancy special tools ,use one old nut has advised has the dismantler (keep for future use ) and the other cut/grind the edges so that it fits through the tapered hole ,drill an hole through centre ,buy a length of threaded stud from an hardware shop ,one nut above 2 below , screw into fork leg push the threaded stud up through yokes/cowl and a large socket which you p[lace on the top yoke ,a few washers on top of the socket run down another nut ,pull into taper and pull up fork leg  with a spanner on the nut bingo tightnen bottom yoke pinchbolt , remove "customised tool" ,insert bright and shinny new one bingo jobs agood 'en!!

Briliant idea thanks. I'm doing my forks as well. I've bought new top nuts so I will use the old ones as suggested.

Neil Ives
Title: Re: Top Yoke and Forks Fused!
Post by: duTch on 12.06. 2012 12:47
Heya Jules,
          And Topdad too,Bad connection here, Yes as Topdad says it works in some cases like mine,  as I have grafted on a  Lightning/Conical front end, and have just looked at the exp.view of the '57 and remember why,as I had this issue with my 'rocket in da '70s ...*problem* *dunno*!!
  Topdads idea is probably good, but in my case not applicable so got a mental block sorry!!
 cheers dutch
Title: Re: Top Yoke and Forks Fused!
Post by: fido on 12.06. 2012 12:56
.....no need for fancy special tools ,use one old nut has advised has the dismantler (keep for future use ) and the other cut/grind the edges so that it fits through the tapered hole ,drill an hole through centre ,buy a length of threaded stud from an hardware shop ,one nut above 2 below , screw into fork leg push the threaded stud up through yokes/cowl and a large socket which you p[lace on the top yoke ,a few washers on top of the socket run down another nut ,pull into taper and pull up fork leg  with a spanner on the nut.....   

I think some bikes had a damper rod attached to the top nut as I found one at an autojumble that already had a tapped hole in the threaded part. I cut the hexagon part off and use it with an old stud in a similar way to your suggestion. I don't bother with the socket, washers etc though. When the fork is through high enough to catch the threads with the proper fork nut I just tighten the bottom yoke pinch bolt slightly to stop it falling back down.
Title: Re: Top Yoke and Forks Fused!
Post by: Topdad on 12.06. 2012 13:25
Fido , you're right , i've now got the same top nut  via george Prew and his excellent damping kit for the A10  which I 'd recommend to anyone ,I found that with the 8" brake working well the forks dipped and bottomed out to easily sorted ,with these fitted no probs  and such good quality that after 6 yrs still as good as the day they were fitted , only looked at 'em on Sunday. cheers BobH.
Title: Re: Top Yoke and Forks Fused!
Post by: Jules on 12.06. 2012 13:35
OK I've got it now thanks for the extra clearing up/understanding - I have been trial assembling my front end so far so haven't actually fitted the shrouds, so now I see the dilemma to come!
There's a good post back some time ago about how to makeup those in fork dampers too btw. I've made some up but have yet to fit them, and found A65 top nuts to have the same thread but with an inner tapped boss for the rod.........
Title: Re: Top Yoke and Forks Fused!
Post by: Jes-can on 13.06. 2012 16:07
So I was able to get the left fork out without too much trouble using a hammer and putting the top nut in and giving it a few hard taps. The right side though is not budging! If the headlight shroud sleeve wasn't there you could at least try twisting the fork itself, but  obviously can't do that. Bugger! At this point the top nut and fork threads are starting to get damaged, so not sure how much more I do it without ruining and having to replace the fork.
Title: Re: Top Yoke and Forks Fused!
Post by: duTch on 13.06. 2012 16:36
Jesse,
     I hope you're using a Rawhide or rubber/ lead/copper mallet or a drift or something in between, not just banging straight on with a hammer-circumstances permitting??
  Also I'm sure you've loaded it with inox or penetrine or yield or something??
     I've found in the past that sitting back with a simple cup of tea helps??    -serious!!
 cheers duTch
Title: Re: Top Yoke and Forks Fused!
Post by: Jes-can on 13.06. 2012 16:43
Went through two cups of tea yes! I have a rubber mallet, but haven't added anything to aid with loosening. I'll pick something up today. After the second cup I walked away from it and decided it would be best to have another go at it today.
Title: Re: Top Yoke and Forks Fused!
Post by: Greybeard on 13.06. 2012 17:41
Heat is great for loosening things. Could you apply a flame from a plumbers blowtorch to the taper area?

Neil Ives
Title: Re: Top Yoke and Forks Fused!
Post by: Jules on 14.06. 2012 11:34
Jesse it sounds like its well stuck in, like a ball joint taper on a car. So a couple of thoughts
 1. maybe you should make up an adaptor like Topdad suggests by turning off the hex of the top nut and fitting a large threaded bolt into it, then you can screw it right down and use all the thread length engagement in your leg ilo just the top few.
2. on car ball joints you have a tool that (trys to) expand the joint and puts it into tension, then you hit the side and top to vibrate the taper and the residual tension "pops" the joint - can you get a small jack between the upper and lower yokes to create the tension, then give it a whack?
3. the soaking with penetrating oil needs to happen at least o'night, a couple of cups of tea wouldn't be enough for that trick to work I dont think  *sad2*
good luck.........
Title: Re: Top Yoke and Forks Fused!
Post by: duTch on 14.06. 2012 16:20
The cups of tea were in the past-but did work then, since then I've grown down and moved on to better bevvies, but don't tell anyone *whistle*

Also the mallet is a bit soft, but just creating a diversion from the angle grinder  *smile*
Title: Re: Top Yoke and Forks Fused!
Post by: Topdad on 15.06. 2012 11:37
Good morning Jesse, you must be pretty p****d off by now , seems you've got an awkward one!! mind you ,probably, once this is resolved everything else will seem a doddle. The use of my contraption won't help with this it's only for reassembley. The other idea idea def heat , we used to call it the silent hammer ,if you haven't any other source buy a small butane torch any hardware shop DIY place will have 'em nothing fancy unless you can see a need for it ,I've had one for 10 yrs only needed 3 -4 times but really useful! Obviously make sure nothing flammable nearby ,bike and in the area around and then after making surre everything is loose on the yokes and that the bottom one has the wedge in it mentioned earlier to ease it ,keep the old nut in screwed in just so theres one/two threads above the yoke top and then heat the top yoke up to has hot has you can get it and then give it a solid smack with a lump hammer , I'm not into butchery but unless someone can think of a more gental way forward ,at this point something drastic needs to be done . Obviously if it moves down to the top yoke undo further and continue but only using mimimum force. If no movement and it's not looking like its moved at all i'd redo the heat try again or then revaluate what you are working with. For instance whats the other side of the top yoke like if it looks damaged is it worth worrying about ,at least there are fine second hand ones around and they don't cost the earth . A thought just occured and someone more knowledgeable than me (not difficult ) may be able to confirm, if you could strip the fork leg down and remove it from the outerleg, maybe you could the just take the stanchion off through the bottom yoke with the topyoke still attched,sorry don't know if feaseable sure someone here can advise...LP.Anyway best of luck ,BobH. 
Title: Re: Top Yoke and Forks Fused!
Post by: fido on 15.06. 2012 11:58
Another idea would be to heat up the yoke then use a watering can or similar to fill the fork with cold water. The rapid contraction of the steel could release it.
Title: Re: Top Yoke and Forks Fused!
Post by: Topdad on 15.06. 2012 12:16
Fido, nice idea ,love people who channel there knowledge to practicable applications ,makes sense and full marks ,kicking myself for not having thought about it , by the way in an old post did you say you are a metalurgist ? if so have you ever worked with my Brother Stan Hebdon from Crewe, He's pretty well known in the industry Best wishes BobH
Title: Re: Top Yoke and Forks Fused!
Post by: duTch on 15.06. 2012 17:25
 With regard to Jules' idea,(ball joint separator),I found this link couple yrs ago, when I was searching for whitworth spanners and figured it'd be useful at least for entertainment
http://www.triumphspitfire.com/Toptool.html (http://www.triumphspitfire.com/Toptool.html)

  have used # 5 which is what caught my eye, but in this case I think #9 may be 'similar' to Jules' idea??
 If not all those ideas are good, but to 'expand' on Jules' idea#2, how about tightening the bottom yoke pinch bolts(otherwise it will just 'slide'), and from the hardware store, threaded rod short enough to fit between top and bottom yokes+ 3 connector nuts (you know the long ones for joining two lengths together??)+use two couplers or similar for locknuts to screw against each other at one end of the rod and against a yoke of your choice, and the other single one other end screw out against locknuts and other yoke, putting yokes under expansion pressure(remember-tightening the bottom yoke pinch bolts), then use all other pre-mentioned options till it cracks-'cept the grinder!!

   Heat but not too much,+
Title: Re: Top Yoke and Forks Fused!
Post by: bsa-bill on 15.06. 2012 18:26
Hi Jesse
Can't recall any mention of fork trousers, if by chance there is none fitted  then could you refit the top nut and use a puller to grip on the bottom of the top joke and place a nut or something similar on the top nut and apply pressure, not a lot to grip on the bottom edge but might work with a suitable puller.
now your going to tell me it has trousers fitted
Title: Re: Top Yoke and Forks Fused!
Post by: RichardL on 15.06. 2012 21:51
First,  I would be concerned about giving a top nut too solid of a whack while the stanchion is stuck.  As far as I can tell,  based on the results of a long ago accident,  they are ductile iron and could bend or distort.  Considering the lack of success so far, I am rather certain that success will only come with trousers or gaitors off (isn't that always the way). Now,  you might try a very large pipe wrench on the stanchion whilst applying the heat, assuming you don't mind hidden scars under the trousers (isn't that always the way). Back to pounding, consider slitting lengthwise a piece of pipe that is the exact length between bottom of top and top of bottom trees. Wrap around stanchion and hold together with hose clamps. Now, when you beat on the nut (with bottom tree clamps loose, both trees will take the force and bending will be half as likely. Also, this means the energy of the whack will not be lost in top tree flexing.  I'll stop before descibing my idea for a puller based on the split pipe.

Richard L.
Title: Re: Top Yoke and Forks Fused!
Post by: RichardL on 17.06. 2012 13:41
Commenting on my own comment,  pounding on the fork nut may also be bad for the bearings.

Richard L.
Title: Re: Top Yoke and Forks Fused!
Post by: duTch on 17.06. 2012 14:31

Which reminds me, how you going with it Jesse, haven't heard update for a while?? If you're still battling, try using a drift (~lump of flat bar~ 25 x10 mm?), and hit hard up against the underside of top yoke with a big hammer, or similar, on top of nut as resistance. This may require 2 people and a combination of some or all other options?
     Another thought is, and I think someone else pointed out that if the bottom yoke 'pinch' is loose enough(?) to slide down and off the bottom, try that.....uhoh yeah remembered is the slider/springs/stuff still on, or can you dismember (dismantle)it??

   cheerrs
Title: Re: Top Yoke and Forks Fused!
Post by: Jes-can on 17.06. 2012 18:52
Sorry I've away for the weekend so haven't touched the bike in a few days. Right side is still stuck, so will try some of these suggestions when I'm back. I'm thinking heat is the next on the list. I'm sure it will come out eventually. Looking forward to having it all apart so I can start restoring it!

On another note. I've got the top end of the engine off and the pistons have quite a lot of scoring on the top and one of them has a small scuff on the top surface. Should I replace them? And I have seen a few sets on Ebay.

http://www.ebay.ca:80/itm/ws/eBayISAPI.dll?ViewItem&item=300710979100&ssPageName=ADME:B:WNAFP:CA:1123

Thoughts? The engine was running ok before I started taking it apart, but if it's apart I might as well do as much as I can so I don't have to do this again for a while.
Title: Re: Top Yoke and Forks Fused!
Post by: RichardL on 17.06. 2012 21:11
A photo of the pistons would be useful. Worst case, I think, might be that the "scuff" was a hot spot that just reached melting point and subsided, but hard to know without seeing. Even on seeing, others here will be better at the diagnosis than myself.

Richard L.
Title: Re: Top Yoke and Forks Fused!
Post by: Jes-can on 21.06. 2012 04:03
Bloody thing is still stuck! I've tried torching it to heat it up and knock it out, but no luck. I have now resided myself to the fact that the fork is buggered so I've started to drill holes through below the top yoke to see if I can force it out from the bottom, but so far it hasn't budged! I'll get it out eventually but wow! Anyone know a good source for replacement forks?
Title: Re: Top Yoke and Forks Fused!
Post by: Brian on 21.06. 2012 04:11
Jesse if you are at the point of being prepared to damage the fork leg then try this.

Firstly wedge a screwdriver or similar in the bottom yoke, then unscrew the top nut about two turns.

Now the good bit, get a hammer and hit it. Now I dont mean a little hammer and when I say hit it I mean give it a good clobber. This will mark the top of the nut so use an old one if you have one.

The top of the fork is tapered, you only need to break the hold on the taper and it will come free. It only has to move a couple of thou to let go.

I've dismantled hundred of BSA forks over the years and have never found one that wouldnt come out.

The trick is to use a heavy hammer and give it a good hit, soft hammers and little taps will not work.
Title: Re: Top Yoke and Forks Fused!
Post by: RichardL on 21.06. 2012 05:59
Brian,

Your post sent me to the garage to look again at the structure of the top yoke. It is not thick and it seems that enough of a whack could fracture or bend it. Maybe I'm dead wrong. Jes' stanchion sounds like it is uniquely frozen to the yoke by rust or corrosion. I suppose that if the thing is going to get destroyed in the process anyway, maybe the huge hammer hit is worth a try, but is there not also a risk of messing up the steering-head bearing races? The stanchions are easier to replace than the yoke, so maybe the route could be to to cut off the stanchion below the yoke and then saw through its remains a couple of times until it gives up.

Richard L.
Title: Re: Top Yoke and Forks Fused!
Post by: Jes-can on 21.06. 2012 06:07
Yes I've already started drilling through it and it still hasn't budged. I'll continue on this route and see how it goes. It's obviously completely corroded where they meet. The bike is in relatively good shape, but I don't think it's been completely pulled apart like this. At least not in a long time. All the other stuff now seems easy in comparison to this issue which really should be simple. It's been fun though and I'm not in a rush to get it done, so I'm not too annoyed by it. I'll keep trying and keep you posted on progress!

Thanks for all the advice so far.
Title: Re: Top Yoke and Forks Fused!
Post by: RichardL on 21.06. 2012 06:17
Jes,

Looking back at your posts, we didn't hear much about you other than "stuck forks". Without prying, would you mind sharing where you are located?

Richard L.
Title: Re: Top Yoke and Forks Fused!
Post by: Brian on 21.06. 2012 06:36
My method does sound brutal doesnt it Richard, but it will work. I have had to resort to it a couple of times over the years. It wont bend or damage anything.

Its a case of sending enough of a shock through the metal to make the taper let go. A bit like one of those hand held impact drivers, you can use a soft hammer or a small hammer and they just will not work, they need a good belt with a heavy hammer to work properly.

Another example would be tie rod ends in cars, you can bash away at them all day with a copper hammer and they will not come apart. Hold a metal dolly on one side and give the other side a good belt with a heavy hammer and they will come apart every time.

"If at  first you dont succeed, get a bigger hammer"  *work*
Title: Re: Top Yoke and Forks Fused!
Post by: muskrat on 21.06. 2012 09:43
 G'day all, how about removing the steering spindle/bottom yoke from the top yoke/stuck leg. Then set it up in a press and use the old nut (it should look pretty second hand by now).
 A nice new set of hard chromed legs arn't that expensive.
Cheers
Title: Re: Top Yoke and Forks Fused!
Post by: Topdad on 21.06. 2012 12:33
Hi Jes, Brian and Richard re my prev post I'm with Brian on this ,always found a 4lb lump hammer worked wonders and didn't do any lasting damage.  I to have never had a set of forks that wouldn't budge but there's always a first. Glad to hear that it's not but you off Jes ,these things are sent to try us and It must get better after you have sorted this! you've more patience than me though by now i'd have ground through the top yoke and started looking for a new one on e-bay or anywhere and has Richard has said probably regreting it has the fork is probably donald ducked anyway .best wishes BobH
Title: Re: Top Yoke and Forks Fused!
Post by: RichardL on 21.06. 2012 15:18
Jes,

I just realized that those of us who have been on here for some time have come to know eachother's experience and recognize it without words, but newer members don't have that advantage. I just want to say that the likes of me (a one-bike rebuilder of a basket case) know that the experience of Brian and others with multiple (or many) bikes deserves high respect. My thanks to Brian for a variety of good advice that's helped me. Paranoia strikes deep, but if Brian says "no harm", he probably knows what he is talking about.

Richard L.
Title: Re: Top Yoke and Forks Fused!
Post by: Jes-can on 24.06. 2012 07:47
Just realized I posted a response in another thread by accident! Anyway. Now having trouble getting the clutch centre nut off! And is there a special tool for removing the other one on the crank the holds the large spring in place?

Cheers.
Title: Re: Top Yoke and Forks Fused!
Post by: Stephen Foster on 02.07. 2012 12:58
Im in agreement with "mannosound" ..there are times Id have been floundering without "Brian"s advice & Id like to take the opportunity to thank Him !!

Regards,
Steve ..
Title: Re: Top Yoke and Forks Fused!
Post by: duTch on 03.07. 2012 09:15
Hi Jesse, I think I noted that you'd jumped another thread to announce success, is that correct??
  Re the clutch nut that's been discussed recently too...somewhere- you'll have to search?
 Re the Hammers, when I mentioned awhile back 'rubber mallet', I think I had in mind genteel things like shafts and like with threads on, and tinware, as I personally have a dangerous propensity for big hammers, a 10 pounder of which can work wonders if used carefully. Bloke I worked for a while back had a 14lb'er- that was fun!! requires good aim.

cheers