June 21, 201412 yr I am hoping someone can enlighten me on the workings of the Cota 247 swingarm, it seems like a dumb question but it is different from any other bike on which I have worked. Inside the swingarm, where it meets the frame, on either side, there is a threaded insert inside of a rubber bushing, a body fit bolt is then inserted through the frame to hold the swingarm in place. Once tightened down the swingarm is locked in place and does not appear to be free to pivot or move. So my question is how does the swingarm then travel through the movement of the suspension? Does it just move with what little flex the rubber will allow, sort of like a torsion system? Or is there something else I am missing? Is there a better method or replacement setup? Such as a bronze bushing/bearing system? Or a roller bearing system? I can make anything I would need since I am a machinist, however I would still like to understand how it was meant to function originally. Also if I were to disassemble and make another setup what should I expect during disassembly? Are the two inserts and rubber bushings seperate pieces? Is there a spacer between the two sides? Is everything just pressed in or is the rubber vulcanized to the metal? Thank you in advance for any light you can shed on this topic. Also if you have an opinion on weather to leave the original setup or convert to another system please comment. This is something that is holding up my rebuild and I need to make a decision on how to proceed. I am also attaching a picture of the threaded insert/rubber bushing setup in the swingarm.
June 21, 201412 yr looks like the rubber must twist , could be good as would prevent shock going through frame , also looks like there is a metal case around the rubber so they would remove , it could be possible to fit the cota 200 bushes ( steel outer brass type inner bush ) look at sammy miller products Edited June 21, 201412 yr by zerorev3rev4
June 21, 201412 yr The centre metal part of the rubber bush should stay still when bolted up (you are saying it does). The swingarm moves against the tosion of the rubber - many british bikes were like this - they feel very stiff with no shock on but work fine. More modern bike (including later Cotas) used bronze bushes and after that most moved to needle roller bearings. Im sure yours will be absolutely fine but if you wanted bushes, In Motion could probably help check sizes. cheers
June 21, 201412 yr Alchemy, I too had a similar problem -and the rear end always felt to stiff .....mine only has a spacing tube (not Threaded). One of my more technical friends made some nylon( he said it was hard wearing and self lubricating) bushes that the swinging arm spindle just passes through - it does seem be better but I also put new Falcons on at the same time. If you decide to make something -i would probably have a set as i've another to rebuild as well - Just give me an idea of cost. And please keep posting - as i'm not the most technical person and although there are a few more 348/9's competing there are not so many 247's. Cheers for now. The Wobbler
June 22, 201412 yr The rubber torsion bush method is quite common on motorbike swingarms and it works fine. It can be tricky to remove them if you ever need to. They do last a long time and require zero maintenance. The original bushes in my 1975 KT250 are still working perfectly. The bushes are also called Silentbloc bushes in industrial catalogues. I recently replaced that sort of bush in my Whitehawk Yamaha swingarm and the replacement bushes were available from a local engineering supplies
June 22, 201412 yr here is a catalogue listing https://www.blackwoods.com.au/search/flexible-bearings-silentbloc/302024107?c=Product
June 22, 201412 yr I think I would leave the silentbloc bushes in. Think you will find them buggers to remove, on my old Triumph Spitfire they used these a lot on the suspension and to replace some of them you end up having to burn them out, believe me the smell of burnt rubber lingers!
June 23, 201412 yr I was lucky ??? my bike was stolen set on fire and recovered so I had no choice. I was struggling to find replacements so the nylon bush set up works and seems to be fine a year on !! Before Torched And now
June 23, 201412 yr I am not sure I would call it "lucky" to have your bike stolen and set on fire! Maybe you mean lucky to have gotten it back and having been able to rebuilt it into a very nice looking machine. Good job! If I had an occasion to remove those old torsion rubber bushings, I would sure try to replace them with real bearings or bronze or nylon bushes. Let the swing arm pivot smoothly and let the shocks do the damping.
June 23, 201412 yr Gents, Thanks for the comments - I was lucky to have a mate or two to help in the rebuilding & "Lucky" was tongue in cheek !!. The suspension was horrible before I put the nylon bushes in - now its just average !!!. I like the idea if some roller bearings but you're never going to make a racehorse out of a camel so you have to stop somewhere. I'm more than happy to put "Off the shelf" mods on - but sadly I'm not skilled enough to do more than that.........although I would happily test some that any one wants "Bashed about" !!!!! Cheers for now. The Wobbler.
July 29, 201412 yr Hi Wobbler, did you use the same swing arm spindle with the nylon bushes?, i have had to cut off my spindle to remove the swing arm, so will need a new spindle when i rebuild, was wondering if anyone knows of a spindle that will fit say from another model or bike. John.
July 31, 201412 yr John, I used the old swinging arm spindle - I would think there will be a few out there if you have a look? I do however think that finding a larger spindle from something else and fitting some roller bearings would be a better idea - it would just mean drilling the holes in the frame out. This is my intention when I do my next one. I'm sure one of the "classic" suppliers could make one . Sorry I can't be much more help. Good luck and keep us updated . I'm in the process of fitting an electrex world electronic ignition - I'll report my findings for those interested. Cheers for now The Wobbler
July 31, 201412 yr Thanks Wobbler, found a place in Spain that can do me a spindle for swing arm, I just have to learn to speak spanish and we are sorted . Also have the chance of picking up another 1978 Cota 247 at the week end, just waiting on a reply from the seller. Interested in the electronic ignition my self. Cheers John.
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