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Allan G, Hillbilly bike
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Original Post (Thread Starter)
by Kev Ev
Kev Ev
Hi all,

I have just recently fitted some new silentbloc bushes to my newly powder coated swinging arm but I think I have not got things quite right.

I think my mistake was not to check the new silentbloc bushes in the frame before pressing them into the swinging arm. I have seen posts about some pattern bushes not being of the correct dimensions and on hindsight I should have paid more attention this, very important area, before fitting them.

Referring to the attached drawing you will see that the side plates on the frame where the swinging arm mounts on my bike measures 9.375" inside.

Am I right in assuming that when the bushes are put together, as shown at the top of the drawing they should measure the same as this dimension on their outer extremeties?

When I pressed in the new silentbloc bushes I made a jig that would allow them to be driven all the way in until the end of the outside diameter was flush with the end of the swinging arm boss. I assumed that when I did this the bushes would be butted up against each other inside the swinging arm, so that when the spindle was fitted and everything was tightened up the swinging arm would be central in the frame. This is due to the inside diameter of the bushes protruding out of the swinging arm by the same amount at each side.

I have ended up with one of the bushes moving into the swinging arm boss more than the other one. I think this is because there must have been a gap in the middle of the bushes and the one that is 'loosest' in the swinging arm has moved when I tightened the swinging arm spindle nut.

I am going to take the swinging arm out of the frame and have a second attempt at fitting new bushes.

I would appreciate the advice and thoughts of anyone who has undertaken this job and can confirm that I am thinking along the right lines and correct in how I believe the bushes should be fitted.


Kev E
Attached Images
Liked Replies
by Kev Ev
Kev Ev
Hi Claude,

You're very welcome. I'm happy if I can help out, as there are so many other BSA owners on here that have done the same for me.

As long as you can get hold of a decent sliding hammer the M10 stud and washers that are required are easy to find.

The adaptor that I made for the right hand side of the swinging arm spindle is, in my opinion, the essential bit to get right. I found that when I got the spindle out, which as I said took some real effort, there was no damage to the threads and this was down to the adaptor being a good fit and kept secure in the end of the spindle by the M10 locking nut and washer at the other end.

I have attached a drawing of the adaptor if anyone wants to make one.

Best regards,

Attached Images
1 member likes this
by Kev Ev
Kev Ev
Originally Posted by GSFROG
Hi, Kevin
)I am about to undertake the removal and replacement job on my swinging arm (BSA A7).
So far the spindle has not moved, in spite of my hammering it hard through a piece of wood.
I would ne delighted to hear how you do it.(maybe with a photo?)

Hi there.

I used a very large sliding hammer along with a piece of 10mm studding and an adaptor to fit in the swinging arm spindle. I locked the stud into the spindle with a 10mm nut on the other end of the studding then fitted my sliding hammer to it and drove it out with this. The adaptor sleeve was made to fit inside the hollow swinging arm spindle with the larger diameter a few thousands of an inches less than the bore of the silentbloc bushes. It still took some effort to remove the swinging arm spindle. The sliding hammer is a very big and heavy unit that I made myself years ago when I used to work on very large CNC machine tools. It was used for removing very large 3/4" dowels from drive racks.

I have attached pictures, so that you can see what is involved. If you need them I can provide AutoCad drawings of all the studding and adaptors.

I agree with the advice about the silentbloc bushes. Do not remove them unless it is absolutely necessary!
Attached Images
1 member likes this
by Tridentman
"Back in the day" when I had BSA A7s and A10s if we needed to change the Silentbloc bushings we didn't even try anything else---just burnt out the bushings and then removed the outer part of the bush using a hacksaw. Then used a new set of bushes and a new spindle.
Just be careful where you do the burning.
Remember this was UK in the 1960s.
No one had a dryer so washing was hung out on lines to dry.
On one occasion we had a big hairy coalman come round threatening to beat us all up because the smoke from the burning bushes had gone onto his wife's washing drying on the clothes line.
Just saying!
1 member likes this
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