ZA7S Carburettors

[trevinoz]

I was cleaning up the carbys for my '50 Star Twin project and find that one of the bowls has been changed.
The carbys are stamped  275 BA/1F and 275 BB/1F which is correct but one has had a type 1B bowl fitted.
The difference is the 1F is longer from the body to the bowl than the 1B.
The '49 model had 275 AR/1A and 275 AS/1A, the 1A bowl being the same as the 1B except for the fuel line connection.
Obviously BSA had a good reason for moving the bowl further from the carburettor. Any thoughts?
After that ramble, I am curious as to what you Star Twin owners have on your machines.
I have found in my bits and pieces a long type bowl, but it has the nipple connection on the bottom and I need the banjo type. I guess I could cross drill the nipple and fit the banjo but the nipple is shorter than the correct type.
Probably be OK if not over tightened.
Another alternative is to change the fitting, but I am not sure if they are cast-in or pressed in. Anyone tried this?
Anyway, back to the shed and get something done before the temperature reaches 40 degrees!
  Trev.

[Brian]

Hi Trev, I fitted 1A bowls to mine because I managed to get a pair of nos ones. They are both the standard length with the nipple type connections but banjo type would be better.

There seems to be some variation in the placement of the fuel taps in the tank and this may influence what set-up you use. On mine there was just enough room to run the fuel line between the carby body and bowl. I have supplied the right carby from the left tap and visa versa. I've added a couple of photos so you can see how I set mine up.

Brian.

[LJ.]

This is pushing me to get on and find another carb for my 1949 plunger Star Twin.

The single carb I currently have on my bike is an Amal 276 DP/1A (left hand side model)

Main Jet 140... Needle jet 0.107... carb bore measures 15/16"

I understand from somewhere that a 176 EC/1B is also reccomended.

Hope this helps!

Oh by the way if anyone has a spare kicking around i'd be ever-so-grateful... 

Cheers!
LJ.

[trevinoz]

It's curious as to why the bowls were changed. Maybe it was to clear the magneto as there is no drip tray.
Trev.

[trevinoz]

Brian, I was just looking at your set-up and regarding your comments re tap placement, could your tank be a later one?
As far as I know, the ZA7 tanks had their taps set at an angle at the rear of the tank, mine does. Also, the pump brackets should be on the bottom of the tank, not on the chain guard.
Pictures of the original fuel lines show them looping behind the carbys and up to the bottom of the bowl, one per side.
Trev.

[Brian]

Trev, there seems to be some some variations in the tanks. I have seen ones with angled taps like you have. Mine has the taps in the same place but vertical, my tank has the fittings for the pump. As fas as I know the later tanks have the taps further forward plus the rear mount is slotted and no tabs for the pump, my 51' A7 has this type on it.

I had a look in the Amal book and the 49' Star Twins had 1A bowls and the 50's had 1F bowls, I'm not sure what the difference is between a 1A and a 1F.

All interesting stuff (or confusing) !

Brian.

[terryk]

Gday Brian, what Amal book are you refering to and where did you get it. Is that the one that lists all side bowl carbs and the bikes they belong to. I have a very faded list but I would like to get a new one if they are available. Also I wish I could send some rain down your way to cool it down and stop those fires we have far too much rain at the moment its a crazy world. thanks Terry

[trevinoz]

Brian, the 1A bowl and 1B have the same dimensions but the 1B has banjo connection and the 1A a nipple.
The 1F has a longer 'arm' than them with banjo connection.
I have a later A7 tank also with the forward taps but the mounts are not slotted.
 Trev.

[olev]

Heres another one for you to chew on.
The bowls are both 1F.
The left body is275AY/1F.
The right body is 275AZ/1F.
Both bowls have banjo feed and the condition and colour of the thing makes me think it could be an original set.
Both carby's have chokes and the throttle cables and choke cables are routed through a two into one thingy.
I don't know what its off. The ratbag I bought my 52 star twin off was going to saw off the inlet manifold and fit it. This ratbag will probably fit a mikuni.

TerryK, Did you see the 48 or 49 rigid star twin basket case for sale in the Cairns Post around Christmas?
He was selling it with a plunger 650 for around two and a half grand .. Its just up the road from you and could be good if you have that sort of cash. (if its not under water)
cheers

[terryk]

No Olev I didnt see that A7 A10 stuff in Cairns post wish I did though I would be up there in a goldenflash. I bet its gone now. We are swimming in rain here at the moment wish I could sent it south to stop those bush fires. Thanks for that Terry

[Brian]

Trev,
It seems that there are a few variations on the tanks. The one with the taps further forward would probably be the easiest to use on a twin carb set up.

TerryK,
The Amal book I have is an original I bought years ago and lists all the carbys and what they fit. I have never seen a copy but they may be available somewhere.

Olev,
Those carby's look like they would be good for a Star Twin, correct size and right /left hand etc.


Brian.

[trevinoz]

Olev, that set-up is the same as mine, complete with chromed junction boxes.
Your set certainly appears to be an original set but the 275 AY and AZ types are not even listed in my Amal book.
Probably a late 1949 mod with the longer type float bowls for whatever reason.
Amal lists 275 AR/1A and 275 AS/1A for 1949 and my set for 1950.
All you have to do now is find the rest of the bike!
  Trev.