Carbs on early Specials

Grewth

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I was following a thread yesterday where the type of carbs fitted to the early ('78/'79) Special models was discussed.
Concensus of opinion was that the BS38 carbs were fitted to these bikes, and the 1980 models onwards got the new smaller BS34 type.
Now I always thought that the European (Special) models always had BS34 right from the start, but I seemed to be in a minority of one.
And sure enough, even Yamahas european sales brochures show the larger type carbs.
OK, so anyone can be misinformed, maybe I'd got it wrong years ago when I first started learning about the XS.

But then I dug out this - Yamahas 3L1 1979 parts list for Europe, quite clearly showing the early type rolling chassis along with BS34 carbs and plastic airboxes.
So I'm not actually going senile after all.
I'm not trying to prove anything by posting this, I'm certainly no expert at building or tuning these (or any) motorcycle.
Just an example of how things get lost and obscured by the sands of time.

I don't suppose this matters in the slightest to most American XS owners - bikes only tend to flow one way across the Atlantic, but it matters to me, as I want my '79 3L1 model (UK market type) to be restored to original spec.
 

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Well, parts drawing and listings can be wrong. The U.S. parts diagrams for the '78-'79 Specials also show the BS34 carbs and plastic airboxes but those bikes never came with them.
 
That's weird.
I've just looked on the rear cover and it says "first edition, Printed in Japan, January 1979"
So that was well before production of the 1980 models started allegedly around August 1979.
I'm thinking that the BS34 is more of an "emissions friendly" carb than the older BS38.
So was the 650 Special sold in Japan ?
Maybe the Japanese home market bikes had them from the start, and the parts list drawings got carried over to other markets ?
 
5000 mile road test article from "Motorcycling" magazine (UK) writen June 1980 but featuring a red August '79 registered bike.
ELJ24V is still live on the UK DVLA system, but it hasn't been taxed since '86.
Apologies for my poor quality photos of photos, but I think you can just about make out the BS34 carbs along with the early type side panel
 

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Seems like I recall at least one other thread where the bike had those euro only BS34's. Note in your pic the fuel line enters the RH carb on the OUTside, and TWO? petcocks North American spec (80 up) BS34's use a single petcock and a fuel tee between the carbs.
 
It's possible Yamaha introduced the BS34's first into a smaller market to "test" a new part and so limit possible recalls, changes to a smaller group of bikes.
This is a fairly common manufacturer strategy.
 
Seems like I recall at least one other thread where the bike had those euro only BS34's. Note in your pic the fuel line enters the RH carb on the OUTside, and TWO? petcocks North American spec (80 up) BS34's use a single petcock and a fuel tee between the carbs.
I was looking at a later set of BS34's yesterday.
As you say, the '80 onwards bikes have a single fuel tap with a T piece between the carbs.
The fuel gallery is left unbored on the carb outers.
The 78/79 tanks all seem to be twin tap.
It lists 2x banjo bolts + banjo fittings in the parts list, so I'm thinking two pipes to the outside of the carbs, straight joining pipe between the two.
 
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