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#896280 11/24/22 4:57 pm
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I previously owned a 1967 BSA A65 (who knows what was original and what wasn't) and I played a lot of games to get the front end from feeling light especially going up hill. To compensate I lowered the Ceriani fork that was on it and put a set of taller adjustable rear Shocks which helped in some ways, but never was a great solution. However, the entire time I owned this one I had a feeling that the swing arm was always a bit shorter than it should be.

I now own a fairly modified 1964 BSA Hornet. When looking at the swing arm all those feelings of it being too short are coming up again. As I recall reading somewhere there are a handful of years where the A65 swing arm is longer. Does anyone know which years and the lengths of the swing arms from those years?


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Without going out in the garage and finding an early swing arm, there were 2 lengths.

Early A50/A65 single carb bikes had a “short” swingarm. Some early dual carb bikes likely did as well from memory. Later dual carb bikes (about 1965 on) had the “longer” swing arm. It wasn’t a huge difference,

IMO, some of what you feel is the position of the swing arm pivot in relationship to the countershaft sprocket. That is long……

Last edited by Rich B; 11/24/22 5:42 pm.

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I can say for definite the early machines (Full chainguard) had shorter. These are distinguishable dint of the fact they have two welded-on brackets on the chainguard side, each having upper and lower mount holes. "Sporting" and other post-'64 had the longer. The shorter version is better for handling I think. Coupled with an 18" front wheel and the later OIF forks, my '63 cafe racer A50 was a beaut to throw around. Oh how we lust after our lost youth lol. The bike has long gone now


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I think the B44GP had a longer swingarm, you can use 2 swingarms cut in the right places and then welded up to make a longer swingarm which is what I did to a C15.

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kommando, did you fit a sleeve inside the joint between the two parts of your lengthened swing arm before welding it to give it extra strength?

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Yes I had an inner tube and the swing arm ends had 45 degree chamfer plus a gap for a generous weld than had good penetration into all 3 parts.

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Originally Posted by Irish Swede
kommando, did you fit a sleeve inside the joint between the two parts of your lengthened swing arm before welding it to give it extra strength?

I doubt it would last 5 minutes without being sleeved.


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This is how I do it for land speed race bikes. Like kommando, inner tube fitted and chamfered to get good weld penetration. I also add a plug weld beyond the end of the inner tube that ensures good weld connecting inner tube with original.

[Linked Image from i.postimg.cc]

And don't forget to use a spreader tube between the flanges at the back to ensure alignment while welding.

[Linked Image from i.postimg.cc]

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Nice welds OT!

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Three inch longer swing arm. Done the same as everyone else.

DA7AA008-DD0C-45E2-9A39-0EC5952FD0D1.jpeg

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I used 2 swingarms to make 1 long one, so only one weld each side but you do end up with enough bits left over to make a mini swing arm ohno .

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Originally Posted by konon
Three inch longer swing arm. Done the same as everyone else.

Looks awesome. How does it handle?


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Originally Posted by Allan G
Originally Posted by konon
Three inch longer swing arm. Done the same as everyone else.

Looks awesome. How does it handle?

The way I did it lowered the bike, so less ground clearance.


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Yes, but again, "How does it handle?"

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I too am curious to hear how it handles. I am debating buying a 70 swing arm and adding two or three inches to it and relocating the shock mounts. Still on the fence about doing anything at all other than some bracing.


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For regular road riding where corners are to be enjoyed leave the swing arm stock, if you intend drag racing or you have boosted power to the point keeping the front down is important, then add length to the swing arm. A65 wheel base is 54 - 57 " , similar to a Manx Norton, this is a sweet spot for handling, go longer and corner speeds will diminish.A longer bike has to lean more for a given corner speed.

Last edited by gavin eisler; 11/30/22 4:49 pm. Reason: more accurate numbers

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Gavin are all A65s a 56" wheelbase?


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Dry frame models are 54.12" , presumably minimum chain , OIF are 57", older A7/ A10 were 56" my mistake. Source ,R Bacon, BSA twins and triples.
My OIF will leave a Ducati L twin trailing on a B road, its flicky compared to the stretched duke , this is all down to wheelbase. The same duc will leave me in its wake when its A roads and top speed matters more.


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I wouldn’t trust everything that Bacon says.

My pre oif is longer than my OIF, though that’s front tyre to the rear number plate (so you could loose a few inches there).

Both bikes handle well but the OIF bikes seem to handle that bit better once you get used to it. From memory the swing arm length on the oif is longer than the pre oif.


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1971 OIF wheel base 56 " in Factory manual.
1970 Dry ,frame wheel base 56 " in factory manual. R Bacon with pinch of salt indeed.


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[quote=MaaseyRacer] and I played a lot of games to get the front end from feeling light especially going up hill. To compensate I lowered the Ceriani fork that was on it and put a set of taller adjustable rear Shocks which helped in some ways, but never was a great solution. However, the entire time I owned this one I had a feeling that the swing arm was always a bit shorter than it should be.

[/quote
My buddy had an OIF Triumph, with the western bars , teardrop tank and 2 teeth off the gearbox sprocket, it felt like you describe, my own bike has shorter forks (2" ), lower bars and rearsets and feels much more planted, the 56 inch wheel base has stuck for years , its repeated across many bikes from Manx nortons, to R1s.Maybe a lead headlight bucket would do something similar to heep the front end down withiut adding unnecessary unsprung mass with tubes and chains, joking , sort of.


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Gavin
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