Swinging arm bearings

Information relating to the Matchless G5 or AJS Model 8 350cc Lightweight
ajsm18
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Swinging arm bearings

Post by ajsm18 »

Hello all,

I've discovered the latest problem with my 'new' 1960 Model 8 is that the swinging arm bearings are worn. I've ordered a new pair but are they easy to replace? One of the 250 frames I had when still trying to build a bike from an engine had a pair and they were an easy push fit in the frame. I assume that they should be reasonably tight in the frame but do they need reaming to suit the swinging arm pivot?

I am rather hoping that I don't have to strip the whole bike down to fix this!

Many thanks for any help

Mark
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Ozmadman
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Re: Swinging arm bearings

Post by Ozmadman »

Not sure how easy those bronze (I think they are) bushes are to replace. I have had the arms off mine but the bushes were fine so I have never had them out. I would presume that they a should be a tight fit in the frame (as my plastic classic Yamaha ones were that I have just replaced with bronze) otherwise they will rotate in the frame. Not heard of anyone with worn bushes before on a lightweight so could it just be a bit of end float? I have heard of those with play(end float) in the arms being cured by loosening the cotter pin on the nearside arm ( this arm is separate to the spindle)then rest a stout lump of wood on the offside arm (this is arm and shaft combined) at the shaft end. Rest the other end of the lump of wood against a wall and then give the nearside arm a heavy whack again at the shaft end and then re-tighten the cotter. Often this is what causes play in the swing arm and they just need a bit of tightening up. Oh and look after the felt seals between arm and bush, if they are still there, as you can't get them. AND.. the swing arm should be lubricated with oil and not grease?? having said that I pumped two small grease guns of gear oil into mine, nothing came out of the seals and no oil dripped out either?? a real mystery as to where it went so I am just presuming that they have sufficient lube?? TO DO... chain guard off plus that little guard extension attached to the primary cover if you can get it off, I couldn't so managed to bend it out of the way but it was tight, rear wheel and chain off, rear shocks off,well lower connections anyway.. that's it, the cotter pin make take a bit of shifting and will probably need a bit of persuasion but it is a bit awkward as the nut faces underneath.

Paul
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
ajsm18
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Re: Swinging arm bearings

Post by ajsm18 »

Hi Paul,

Thanks for the info. I hoped the swinging arm bearings would be easier to replace than you describe but I'll and and see if there is anything I can tighten up first!

Why, oh why, did I want to try a 'lightweight'... :headbang:
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Les Howard
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Re: Swinging arm bearings

Post by Les Howard »

Surely all you have to do is to knock in the new frame bushes and then try to fit the spindle? If the spindle goes in, even if slightly stiff, that will do. However if the spindle does not go in then the bushes will need reaming, but surely this will be an easy task? using a reamer will be the same as fitting the spindle....Les
Phamiltoneddy
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Re: Swinging arm bearings

Post by Phamiltoneddy »

There is an article on replacing lightweight swinging arm bushes in the archives. Here is a link to it:

https://www.dropbox.com/sh/1311siupow1d ... d.pdf?dl=0

The spindle is welded into one part of the swinging arm so, if it is worn, engineering skills are required. I believe Andrew Engineering (Leigh) Ltd offer a spindle replacement service.

The swinging arm on my 250 CSR has excessive play and I shall be trying to remedy this in the course of the next month or so. I shall initially try the "loosen cotter pin and whack end of swinging arm with heavy mallet" proposal mentioned above but, if that doesn't work, I shall resort to the procedures described in the archive article.
ajsm18
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Re: Swinging arm bearings

Post by ajsm18 »

Thanks for the replies and suggestions. It may be that I'm worrying unnecessarily but we'll see. I have a habit of taking things to bits and then taking a long time to get them back together!
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Ozmadman
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Re: Swinging arm bearings

Post by Ozmadman »

ajsm18 wrote:Hi Paul,
Why, oh why, did I want to try a 'lightweight'... :headbang:
Because they are nice bikes and greatly underestimated in my opinion, things wear out on any bike and these are easier than many to work on ( may revise that last statement when I come to unravel my engine knock scenario) but LIGHTWEIGHT??? NO!! .. The winter weather now is upon us so any work on the bikes for me is based on whether it is raining or not as I have to work outside, well, take bits off outside and then do the work in my kitchen.. if you have a garage count yourself fortunate as this time of year is so frustrating for me as I end up having to do work in the summer when I should be riding!!..

Paul
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
ajsm18
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Joined: Sat Jan 01, 2000 12:00 am
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Re: Swinging arm bearings

Post by ajsm18 »

Ozmadman wrote: The winter weather now is upon us so any work on the bikes for me is based on whether it is raining or not as I have to work outside, well, take bits off outside and then do the work in my kitchen.. if you have a garage count yourself fortunate as this time of year is so frustrating for me as I end up having to do work in the summer when I should be riding!!..

Paul
Hi Paul,

That sounds bad! In my formative years I did all my work either under the street lamp outside our house or in the back garden! That was great way to learn about AJS singles! Nowadays I do have a garage but it must be about 50 years old and the asbestos roof sheets are so cracked the bikes get a bit damp in periods of wet weather. Thank goodness for ACF50!
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Ozmadman
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Re: Swinging arm bearings

Post by Ozmadman »

ajsm18 wrote: Thank goodness for ACF50!
Yep, my two bikes the model 8 and a 1974 Yam RD250 that I have just spent a packet renovating will get the ACF 50 treatment soon, hoping to be able to go out on the YAM a few more times before it is retired for the winter (it's too nice to be subjected to the snow and salt, there's too much chrome on it!!!) The AJS wont get ridden again until I sort out what the engine knock is and the YAM is ok but has developed a gearbox noise so that will need to be investigated at some point too, once the AJ is sorted. BTW do you cover everything with ACF 50?? I am a bit worried whether it will affect the paintwork etc, I just put it on all the chrome stuff at present. Both bike are double covered with waterproof covers and the AJS has had 3 winters outside and has not been affected, maybe all that wind and fresh air is not so bad as long as it stays dry under the covers.

Paul
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
Andy51
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Re: Swinging arm bearings

Post by Andy51 »

Hi Mark, I wrote an article on replacing heavyweight swinging arm bushes that was in the Jampot recently, the same principles presumably apply to lightweights. You should be able to pull the old bushes out using stout threaded bar and spacers, ditto to put new ones in. To avoid bushes closing up (and thus needing reaming) I turned them down to be a push fit and used Loctite - can't remember the grade but it was in the article. Hope this helps.
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