Author Topic: Front forks rebuild parts  (Read 2853 times)

Online Jules

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Front forks rebuild parts
« on: 07.06. 2011 07:46 »
Well I've established that the top and/or bottom yokes are bent/twisted which is causing my leading/trailing forks, does anybody know where I can get replacement top & bottom yokes that are straight please*sad2*

Offline MG

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Re: Front forks rebuild parts
« Reply #1 on: 07.06. 2011 07:51 »
Hi Jules!

If you have access to an oxy-acetylene kit it is possible to heat them locally and straighten them out. I've done it on several without any negative effects (except the need for re-painting obviously). Best to have the bike there as well to trial-fit and correct them until you are happy with the result.

Cheers, Markus
1955 A7 Shooting Star
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1961 Matchless G12 CSR

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Online Jules

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Re: Front forks rebuild parts
« Reply #2 on: 07.06. 2011 09:08 »
thanks Markus, the problem I have is that I dont actually know whats straight on the bike! I paid to have the frame straightened yonx ago but now I look at it it doesn't look right at the swinging arm (see my earlier posts) so I decided to assemble the front and rear wheels/suspension and run a line down to see how it actually shaped up. I have new front fork legs and bushes etc but found that the front legs were not parallel etc, so now I've assembled the front forks off the bike and can see that the top/bottom yokes are not parallel to the wheel axle, but I cant actually see whats bent specifically, only that one leg slides nicely through both the yokes, while the other is tight, as if one side of both upper and lower yokes are twisted. Also cant tell if the centre spindle is bent either!!!!!
I do know that the fork legs were ridiculously bent when I bought the bike, so suspect that the force had transferred up through the yokes and maybe the spindle. If it sounds like a mess, it was! Only thing I can think is to check each part somehow, or replace the parts....
I did think about taking the assembly to a job shop and having them rebore the bottom yoke in line with the top yoke (the clamp should allow this I think), but then how to check the centre spindle is straight??
any ideas very welcome, thanks 

Online BSA_54A10

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Re: Front forks rebuild parts
« Reply #3 on: 07.06. 2011 11:20 »
Get a copy of the frame diagram and start measuring.
A lot of "Frame Straighteners" simply twist the frame to make the front & back wheels in alignment so the frame can be bent and then the swingarm is bent incorrectly to make the bike run straight.
I have a 1973 A 65 which was "straightened" it rides quite fine but the swingarm pivot can not be removed as it is bent to a zig zag shape
Bike Beesa
Trevor

Offline muskrat

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Re: Front forks rebuild parts
« Reply #4 on: 07.06. 2011 13:24 »
G'day Jules,
                if you can make a long (as long as the fork legs) shaft that's a neat slide fit through the center spindle and just clamp both legs in the bottom yoke you should see if the spindle is bent. I would use the good side as a reference and tweak the other side as MG suggests.
Quite often see them on ebay but they could be bent as well.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Muskys Plunger A7

Online trevinoz

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Re: Front forks rebuild parts
« Reply #5 on: 07.06. 2011 22:30 »
Jules,
             I have assembled the top and bottom yoke and held them horizontally in a vice then offered up the stanchions.
With a spirit level and rule I soon found the culprit which was a slightly twisted top yoke.
It only took a bit of work with a large shifter to get it back into plumb.
However, sometimes badly bent yokes can stretch and are then scrap.

  Trev.

Online Jules

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Re: Front forks rebuild parts
« Reply #6 on: 08.06. 2011 07:04 »
both good ideas guys, you make it sound as though you can bend them relatively easily, can you do this without heat? they seem very robust castings/forgings..........cheers

Offline RoadRunner

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Re: Front forks rebuild parts
« Reply #7 on: 08.06. 2011 20:19 »
Hi Jules,
Does anyone nearby have a spare set of yolkes you can borrow to see if that resolves your problem??
You've not listed whereabouts you are in the world in your profile - it may assist you in finding that friendly forum member willing to help? I've some spares including yolkes - PM me if near the Midlands - UK.

Cheers
RoadRunner

Online trevinoz

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Re: Front forks rebuild parts
« Reply #8 on: 08.06. 2011 22:20 »
Jules,
             The old saying goes something like "With a long enough lever, you could lift the world."
The bent yokes that I have had were only slightly out but at the end of the stanchion the effect is greatly magnified.
I did them cold but there was not much needed, as I said.

  Trev.

Offline wilko

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Re: Front forks rebuild parts
« Reply #9 on: 09.06. 2011 01:08 »
They're usually malleable iron so just do it cold and stop being a chicken!

Online Jules

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Re: Front forks rebuild parts
« Reply #10 on: 10.06. 2011 14:02 »
thanks again everybody, and yes Wilko I am a bit of a chicken when it comes to something like this. Brute force doesn't sit well with me but I can see that I dont have a lot of choice it seems in this case  *sad2*. I think its because there is no going back once I get into it and so far I haven't managed to locate any replacements should the need arise. Trev's experience suggests that maybe I'm being overly concerned about finesse with this, so here goes...............
BTW does anybody know the difference between plunger and swingarm front fork yokes?? I have some parts feedback on the 65-5448 & 66-5089 parts which the book says are for plunger, swinging arm parts are 42-5035 & 42-5012, will they fit or stuff things up for me if I use plunger parts on my swinging arm? cheers

Offline muskrat

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Re: Front forks rebuild parts
« Reply #11 on: 10.06. 2011 15:42 »
Not 100% sure (it's 12:35AM) but I think the only difference is the steering lock hole. The Stanchions fit both, cups & cones are same, shrouds should fit too.
Just thought the steering stops might be different. Will look at mine tomorrow (today!).
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline RoadRunner

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Re: Front forks rebuild parts
« Reply #12 on: 10.06. 2011 16:39 »
Hi,
The BSA parts manual gives the part number 42-5035 for SA models; 65-5448 for the plunger - the diagram doesn't show the steering column lock niether does it show speedo mount holes but these are shown for the A10 Road Rocket with part number 42-5036.
But the set in pics below (42-5035) does have the lock and speedo mount holes; these are also the same as fitted to my plunger - stops work fine?

RoadRunner