Author Topic: A worthwhile modification  (Read 799 times)

Offline morris

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A worthwhile modification
« on: 02.06. 2017 21:48 »
I was never happy with the SA's road behaviour at the rear end so I decided to take the swingarm out and have a look at it.
The rubber bushes were worn as one might expect, but I found the swingarm wasn't all that good either.
It had worn by about 3-4 mm at the left, which explained why the left arm was rubbing against the brake pedal spring.
I decided to mill the opposite side down to have both sides of the same length so the swingarm would be centred in the frame again.
I then turned a couple of bronze bushes with a 4 mm shoulder and two polished steel inner bushes to a tight fit over the hollow spindle and line reamed the bronze bushes to a 0.003" tolerance . I had made the inner bushes so that they stuck out by about 0,3mm both sides for them to clamp between the frame.
A grease nipple finished it off.
This completely transformed road holding. From a wobbly back end to driving on rails.
'58 BSA A 10 SA
'52 BSA A 10 Plunger
'55 MORRIS ISIS
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Online KiwiGF

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Re: A worthwhile modification
« Reply #1 on: 02.06. 2017 23:03 »
Good post. If I had the skills I would have done this....but I had to use new silent blocs instead  *sad2*
New Zealand

1956 A10 Golden Flash (1st finished project)
1949 B31 rigid “400cc” (2nd finished project)
1968 B44 Victor Special (3rd project,in progress)
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Offline coater87

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Re: A worthwhile modification
« Reply #2 on: 03.06. 2017 03:07 »
 Excellent post, if I would have known I could do this I would have!

 But instead I put in new silent blocks also.

 If I had to install those for a living, I would quit and move into a hermit hole and eat roots and berries instead. 
Central Wisconsin in the U.S.

Offline jachenbach

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Re: A worthwhile modification
« Reply #3 on: 03.06. 2017 03:33 »
Very nice piece of work.

Online Kickaha

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Re: A worthwhile modification
« Reply #4 on: 03.06. 2017 04:00 »
I like it lots, I've been considering something like that for a while, a complete lack of machining skill is the only thing holding me back  *smile*
1955 BSA Gold Flash
New Zealand

Offline muskrat

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Re: A worthwhile modification
« Reply #5 on: 03.06. 2017 11:41 »
Yep, 1st thing I did to the A7SS racer in "91. With that and taper steering head she out cornered featherbeds.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline morris

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Re: A worthwhile modification
« Reply #6 on: 03.06. 2017 21:38 »
Yep, 1st thing I did to the A7SS racer in "91. With that and taper steering head she out cornered featherbeds.
Cheers

Credit to the one who deserves it. After all it was you Musky that got me in to it.
 *beer*
'58 BSA A 10 SA
'52 BSA A 10 Plunger
'55 MORRIS ISIS
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Online RichardL

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Re: A worthwhile modification
« Reply #7 on: 03.06. 2017 21:51 »
So, is this saying that metalastic bushings do no real good for vibration damping and softening of swingarm swing, or, is it that this mod is mechanically more positive and that outweighs the benefits of damping?

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Offline morris

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Re: A worthwhile modification
« Reply #8 on: 03.06. 2017 22:51 »
So, is this saying that metalastic bushings do no real good for vibration damping and softening of swingarm swing, or, is it that this mod is mechanically more positive and that outweighs the benefits of damping?

Richard L.
Good point Richard. I was also having some doubts at first but found that, after tightening the hollow spindle nut and greasing the lot up, there was a noticeable damping effect. Combined with the new shocks this indeed gives a mechanically more positive feeling but absolutely no sign of the rear end bouncing around. I have tested the bike on some rough road surfaces and it felt incredibly well.
Only question is, will it stay like that, or will wear set in quickly? Only time will tell.

'58 BSA A 10 SA
'52 BSA A 10 Plunger
'55 MORRIS ISIS
The world looks better from a motorbike
Belgium

Online Peter in Aus

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Re: A worthwhile modification
« Reply #9 on: 04.06. 2017 01:48 »
Good one Morris, I will be doing that to my A10 if I ever have to take the SA out for any reason, I think it is a good idea especially for the crossover brake models as the inner sleeve of the metalastic  bush has to be held tight so as not to turn, almost impossible as there is not much rubber between the inner and outer sleeve of the bush. *good3*
Peter

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49 A7 longstroke
58 A10  SA

Offline edboy

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Re: A worthwhile modification
« Reply #10 on: 04.06. 2017 02:33 »
i ve used the same needle race bearings used on the late bsa singles. straight fit but with the cross shaft you have to have a long hollow sleeve ground to fit that goes between the needles and the cross shaft spindle, grease nipple and proper spacing a must but worth it. the rear shocks start doing the damping.