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B175 Swinging arm pivot pin bolts
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Acrhodes
Oxford
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January 13, 2020 - 4:15 pm
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I recently purchased a 1970 B175 and am now engaged in some winter maintenance. On the list was the replacement of the swinging arm bearings, but having read a number of the forum posts I will really ensure they need doing!

However, I am already puzzled. My spares list tells me I should have 7/16" UNC drilled-through bolts with grease nipples, but what the bike has are a square ended "studs" (no through drilling or grease nipples) and lock nuts. (See picture)

Can anyone throw any light on this?

IMG_7047.jpg

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NeilB
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January 13, 2020 - 6:14 pm
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Looks like a cast iron pipe fitting to me

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stubaker58
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January 13, 2020 - 8:56 pm
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Yes, that’s definitely not standard! 

D7/14 hybrid (4 speed with D7 crank etc.) on the road, D10 Bushman awaiting rebuilding.

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AdrianS
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January 14, 2020 - 2:30 pm
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Have you tried undoing them?

Would be interesting to see whats underneath!

Do you need to replace the bushes? Is there excessive play or side to side movement?. One problem by not removing the nuts is that you don't know if there is any grease present for the pin.

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Sponge
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January 14, 2020 - 7:11 pm
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Hang on.......I would like to have a closer look. It looks as though the swinging arm bolt might be right but instead of the grease nipple there is some sort of radiator bleed screw fitted.   

The question is - is there any play in the swinging arm bushes - if yes then it needs to be stripped out and replaced with, ideally, the correct bushes, pin and bolts (C/w grease nipples).  

If no play in the swinging arm bushes - then just try to unscrew the rectangular/square thing and tell us what you discover.  If it comes out OK then it might be OK to fit grease nipples and give it a good greasing up before 'ride on dude'. 

Hope this makes sense

Sponge

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Acrhodes
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January 15, 2020 - 3:22 pm
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Thanks for all your comments.

I have dismantled it all now as there was lateral play in the swinging arm.

My original photo did not show it clearly but it is not a bolt with the square screwed into it but a threaded stud that ends in a square. What looks like the bolt head is a locking nut.

I knew I would need to change all this as there was no means of greasing the bushes so I now have the bolts and pivot pin removed but have yet to remove the bushes from the swinging arm. The "bolt" arrangement looked original and I must admit I have a very vague recollection it was the same on my D7 in the sixties (but that was a long time ago!). There were no shims in place.

I will be buying new bolts/grease nipples, shim set and probably a new pivot pin (I have the bushes). Is there a preferred source for these?

The pivot pin can be easily pushed back into the frame tube for a couple of cms and then stops. Is it gripped only on the inner edge of the sleeving in the ends of the frame tube?

Any insights would be most appreciated!

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NeilB
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January 15, 2020 - 5:02 pm
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The ends of the pivot pin will wear a small amount, even though it's supposed to be the bronze bushes that wear. If it's not too bad then you can get the pin ground, but if it goes easily through the frame then by the time you'd ground it, you wouldn't have the tight fit that you need. 

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Acrhodes
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January 15, 2020 - 5:37 pm
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I've added a photo now showing this "bolt" in its two parts, hopefully clearer.

If these were ever correct parts I can imagine how they would work; The internal thread in the pivot pin stops short of the radial grease hole, so if you packed the pivot pin cavities with grease then screw in this stud it would force grease through the hole to the inner surface of the bush. IMG_7065.JPG

These "special" bolts are 7/16" and 26 tpi (B.S.C?) so I'm going to get a new pivot pin as well to ensure all parts are compatible. Thanks for your help.

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AdrianS
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January 15, 2020 - 6:55 pm
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The bushes are fitted inside the frame and in each end of the swinging arm and then the bolt is pushed through with any shims in place between the frame and swinging arm. The pivots have a tendency to seize and any internal rust build up can make them difficult to remove. They often need a bit of help with a hammer or even a press to remove them. If you are going to replace the pin and bushes don’t be shy of using a bit of force to shift the pin.

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Sponge
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January 17, 2020 - 8:46 am
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For the sake of accuracy it might be worth looking at a BSA parts diagram - it shows the components clearly.

The best advise I can give you is to take your swinging arm to a classic motorcycle specialist who has the gear ( a press, reamers, extractors and measuring equipment etc). The swinging arm Bantams are the same procedure as the C15 swan necks, so it is not unique.   

But if you want to have a go yourself then ..........

The pin is meant to be a very tight fit in the frame lug.  There should be no bush in there ( unless it has been bushed as a repair in the past). 

I would advise you not to hammer the pin out  - excessive hammering will splay the ends of the pin and when you hammer it through the frame lug it will widen that as well causing expensive damage.  Try to find a local garage, or workshop, or friend, with a press and have it pressed out properly.  In this way you do no further damage to your bike.      

The swinging arm bushes can be extracted by careful cutting with a junior hacksaw in two, or three places to collapse them inwards but be careful not to damage the meat of the swinging arm itself. 

You can purchase all the bits from a range of suppliers but be aware that cheapest is not always bestest.    

The new swinging arm bushes should be wound in using the 'two sockets and a threaded rod' technique - discussed elsewhere in this forum.   

Once the new bushes are in place , insert the pin and check for a nice smooth fit with no play - be prepared to have it all line reamed if it doesn't fit right.   

When you are happy with it I would also advise checking the swinging arm for straightness and distortion whilst it is on the bench. Most swinging arms that I have stripped have been bent or splayed and have needed a bit of TLC to get them back to their duty.   Once again a specialist job. 

Once happy it can be assembled - check clearances for shims before you drive the swinging arm pivot pin into its hole.  Once again a press is the correct way to go about it but if you have to use your own resources then make sure you use a rubber mallet and a drift that is softer than the swinging arm pivot pin.   If you hammer the end of the pin you will splay it enough to end up with it not going into teh bushings and hence have to start all over with new parts. 

Sorry this is a bit long winded but if you make a «censored»-up of your swinging arm bushes you will have to take the bike to pieces again quite soon and do it again, and again etc. From bitter experience ( I have owned and ridden Bantams since 1974 - ), the swinging arm is something that you need to get right first time and its worth getting an expert to set it up for you.   

Sponge

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AdrianS
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January 17, 2020 - 9:38 am
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Good reply Sponge,

 

I did manage to tap mine out with a hammer but agree with you if the pin is very tight then a bench press will be needed.

I managed to hammer mine out as the bike was still relatively intact and wanted to just remove the swinging arm. My frame had been "bushed"

sometime in the past. If you need to use a bench press then the bike will probably have to be stripped to the bare frame.

My B40 (similar arrangement ) needed pressing out as the swinging arm had seized so couldn't even be moved by hand ( I had just bought the bike as a project). The chap who did it for me said his gauge read nearly 2.5 tons of force before the pin moved!

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NeilB
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January 17, 2020 - 10:44 am
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Sponge said
The new swinging arm bushes should be wound in using the 'two sockets and a threaded rod' technique - discussed elsewhere in this forum.   

Just as a note, be careful when doing this as the rod can try to "wander" and not pull the bush in straight, I pressed mine in with sockets and my big bench vice. I well expect to need to do mine at some point with either a new pin, or ground pin and bushed frame. 

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Sponge
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January 18, 2020 - 10:25 am
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NeilB is dead right - if you have a vice that is big enough to do the job (pressing in the swinging arm bushes), it is preferable but take care to make sure everything lines up before you start to add armfuls of torque to the task. 

Once you get these bushes and pin right you will have big peace of mind when building the rest of the bike.  I would much rather do a full engine strip than have to replace swinging arm bushes - as George Gibson, a brilliant BSA engineer from Altrincham Cheshire,  once told me  "bring it in here so we can get that right first time lad - you don't want to do it twice"        

Sponge 

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Acrhodes
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January 18, 2020 - 4:00 pm
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Thank you all very much for helpful advice!

I managed to get the bushes out without cutting them, tapped them out with an aluminium drift machined to suit.

The pivot pin also came out fairly easily and I hope to refit a new one in the same way as the bike is not fully stripped down.

Thanks for the advice on fitting the new bushes, I had been pondering which way would be best. I have a large vice and I will probably machine up a short aluminium mandrel to help align the bushes with the swinging arm at the start of the operation.

I need to order a new pivot pin and the special pivot bolts but I've been a bit confused over which one to use for my bike (1970 B175). My parts list says it is threaded 7/16" UNC (82-9915), but I've seen "fine threaded" ones on offer, and my existing one has a 26 tpi thread. 

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