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Micha
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I do recall that there was once a topic here about this issue, but I cannot find it.
I need to take apart the left side, as the plunger's for slider doesn’t want to insert to the its place.
Need to see what is going on inside.
Thank you in advance.

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

Micha
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Should be "plunger's fork",

Should be "plunger's fork", of course.

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

wa1nca
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plunger shaft (fork)

does the plunger shaft #23 go down but stops about 1 1/2 inches and wont go all the way ??
If so then the 2 washers #18 and #19 are not line up even and the shaft cant go all the way down
I had the same problem
I used grease to glue the washers together and it then seated all the way to the bottom
Also make sure the grove on the bottom of the shaft is positioned correctly so the bottom bolt can be inserted and tightened down

https://www.bmwclassicmotorcycles.com/parts/all-parts/rear-suspension/

Tommy

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Tommy Byrnes
54 R51/3 55 R50 64 R27 68 R69US 68 Sears Allstate 250 (Puch)

Micha
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Thanks wa. I also saw it

Thanks wa.
I also saw it coming and greased those washers before trying to insert it!
That's not the problem as the rod will not reach that area. Long before it gets stuck, which makes me wonder if there’s something not straight… anyway I am considering to take them apparat for a total cleanup, inspection and lube.

The question is – how?

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

wa1nca
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Plunger Shaft

I would take out the axel holder #1 from the frame and see if you then can insert the shaft #26 all the way
If not maybe have a bur on the shaft or in the top bushing
unlikely the shaft is bent

https://www.bmwclassicmotorcycles.com/parts/all-parts/rear-suspension/

Tommy

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Tommy Byrnes
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Micha
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Tommy, I appreciate your

Tommy,
I appreciate your time.
I should have mentioned that the rear plungers are taken of f the bike.
I am trying to figure out how is it possible to turn the spring out from the aluminium bracket, all this with the cover in my way...

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

wa1nca
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spring removal

I dont have my manual with me as I left it with the person doing the pin stripping of my tank and fenders
It is not easy and I think you may have to cut a hole in the spring cover so you can take a punch and drive it free
I did not do mine because of this and probably only has to be done if you wanted to replace the spring with a heavy one for side car use
should have my manual back next week

Tommy

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Tommy Byrnes
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schrader7032
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Don't know if this helps any,

Don't know if this helps any, but Tommy's post made me think of the shop manual I have for my R25/2 with a plunger rear end. There's a small paragraph that is titled "Removing rear suspension spring from housing cover". It says that through a drilled hole of the spring covering tube, catch spring end by means of a pin spanner Matra No. 284 and turn spring off the bearing plunger case integrally with the housing cover plate. The tool is described for use on the bell-shaped cover on the Cardan shaft. Guess it has multiple purposes.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Micha
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Thanks a lot guys. I

Thanks a lot guys.
I understood and will try it.
Seems to be a hard one.

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Michael Steinmann
R51/3 1952
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wa1nca
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Rear springs

Kurt that is correct
But after 50 years the spring cover #15 gets frozen and is unable to turn and will most likely get damaged beyond repair if removed
I would leave the spring in place unless you find you have to replace the plunger bushings # 16

Tommy

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Tommy Byrnes
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Micha
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Well, it was easier than I

Well, it was easier than I thought. I made my regular penetrating stuff (which is
a half and half mixture of ATF and acetone) and soaked it overnight. Then took my good old ridgid pipe wrench and turned the cover, that I wrapped in a cloth to prevent scratches. It turned very easy and I managed not to deform it. Then I exposed the end of the spring through that hole/window and knocked it free with a punch.

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

wa1nca
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Removal of plunger spring

Good news
I was led to believe that the cover would be damaged

have to found out why the shaft would not insert all the way yet

Tommy

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Tommy Byrnes
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Micha
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I've already had a chance to

I've already had a chance to check Mark's site for this rear plunger's bushing (Nr. 16); according to his system they are described as pertinax items, which is AFAIK some kind of composite material, while my machine has bronze one fitted. Are bronze items still available?
Is the bronze bushing the original correct ones and the pertinax is just an Improved replacement? I'm afraid that pertinex will collapse while inserting them into the bracket. I know I will not be able to involve heat while assembly. Are there any special instructions for installing them?
It could be that my bronze parts are old replacements that where fitted by previous owner?

  • btf_33_0991.jpg
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Michael Steinmann
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Micha
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Another thought is that maybe

Another thought is that maybe the shaft is not straight anymore. And then what? I assume that fixing it is not worth it…

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

wa1nca
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Bushings

Yea Salis site also says pertinax also see details
They also would need to be reamed after installation
I wish I had my manual back maybe next week

https://bmwclassicmotorcycles.com/index.php/bushing-rear-suspension.html

To check the runout of the plunger shaft you need a flat surface (a piece of glass works well) and roll the shaft on the surface
if it is bent you will see it

Does the other shaft also not fit all the way
they are the same for both sides
If so check for any burs on the shaft

Tommy

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Tommy Byrnes
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Micha
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Well I checked on a straight

Well I checked on a straight surface and it is slightly bent. About 1mm.
The question is whether such a hollow rod can be straightened or is it better to buy a new one?
A new slide and two pertinax bushing are a 100 $ over at Mark Huggett before shipping.
And there's still the question of how to install these pertinax.
I asked over at Huggett with no reply.

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

wa1nca
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Plunger shaft

1 mm bent
that seems way too much
have you checked the other shaft also and if it will fit into left side axel holder

Tommy

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Tommy Byrnes
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Captonzap
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Bent tubes can be straightened.

Front fork tubes on telescopic forks are straightened all the time.
You will need three saddle blocks and a press, and some one with some experience to know where to place them.
Or, find some tubing about the same size, bend it, and then try to straighten it.
Gentle bends can use the blocks further apart. Sharp bends need the blocks closer together, and more pressing force.
Practice on some scrap, and you will find out a lot about what it takes to unbend the tube without inducing secondary bends.
Another learning practice is to take some straight 6mm copper tube, and bend it. Then, using your fingers, try to return it to straight, as straight as it was to begin with. This will teach you a lot about where to place the pressure and the support.
CZ

Micha
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Thanks a lot.

Thanks a lot.

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

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