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D1 Carburettor identity
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Hans Kreuzen
Queensland Australia
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July 25, 2018 - 9:18 am
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Aquarius said
I think that is a 261 (not a 361), they were fitted to very early D1 Bantams (up to 1950?).

The only difference I know of is the float chamber top, the 261 is threaded and the 361 is fitted with 2 screws.

They are very similar and the parts that Burlen keep should fit either.  

This is correct

1950 D1 plunger for daily use, Concourse 1948 D1 rigid, 1949 Aus. PMG replica D1 project and a 1949 rigid D1 survivor.

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Hans Kreuzen
Queensland Australia
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July 25, 2018 - 9:22 am
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lbayorkie said
Thats good I think all 1949'ers has 261's but I was wondering whether my engine came out of the factory with a 261 or 361.  

 Your 49 would have come out with a 261 

1950 D1 plunger for daily use, Concourse 1948 D1 rigid, 1949 Aus. PMG replica D1 project and a 1949 rigid D1 survivor.

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Hans Kreuzen
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July 25, 2018 - 9:33 am
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lbayorkie said
Do we know when in 1950 the 261's were replaced with 361's? I think my engine (26554 YD) left the factory in 1950 and although it is now fitted with a 361 (serial 4586) I would like to know if this is what was originally fitted. Are there records that may reveal this?

Alan  

I am not sure, but I have a 361 on my 1950 plunger and I would presume that half way through the year in 1950, BSA would have changed over, As the screw type 261 where hard to open, there is absolutely no difference apart from the 2 screws holding the float bowl lid down.

I have a untouched December 1949 rigid that has all the features from the newly released 1950 model. BSA used the next engine and parts in line during assembly with no order.

HTH, Hans

1950 D1 plunger for daily use, Concourse 1948 D1 rigid, 1949 Aus. PMG replica D1 project and a 1949 rigid D1 survivor.

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lbayorkie
Otley, West Yorkshire
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September 10, 2020 - 8:40 pm
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Aquarius said
I think that is a 261 (not a 361), they were fitted to very early D1 Bantams (up to 1950?).

The only difference I know of is the float chamber top, the 261 is threaded and the 361 is fitted with 2 screws.

They are very similar and the parts that Burlen keep should fit either.  

In fact they are different in one other way. The orifice for the brass nut which shields the jet is a different size and so therefore is the nut

I took the 361 off  my Bantam today and replaced it with a 261, however fuel leaked out of the washer on the aforementioned nut. I tried to fit the washer from the 361 (which I knew to be good) but it was too small. I tried the nut and that was too small as well. 

The Amal website only seems to have one size of washer for the 261 and 361 which seems strange. Oh yes, one other thing there are two holes where fuel comes out when the carb is tickled.

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lbayorkie
Otley, West Yorkshire
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September 11, 2020 - 9:08 pm
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I spoke to Amals technical section today and explained the problem. They spent 15 minutes looking through their records and concluded that all 261s and 361s had exactly the same jet plug size, hence they only supply one size washer as a replacement. Mine is definitely stamped 261/001D so I don't know whats going on because it definitely bigger but in other respects is identical.

Also, every 261 or 361 I have seen has had a fibre washer on the jet cap, but Amal told me the original spec is for a metallic washer (think they said brass but could have been copper) and this is what they supply as a spare.

You will have to draw your own conclusions!

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GlenAnderson
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September 12, 2020 - 5:30 pm
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My conclusion would be that someone, sometime in the last 70 years, replaced the plug with an oversized one because of previous hamfistedness, damage, poverty, incompetence or simply because it was what they had to hand. 

Overthinking things is often a bigger obstacle to progress than the actual obstacle. 

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lbayorkie
Otley, West Yorkshire
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September 12, 2020 - 5:39 pm
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Thanks  you are right we may never know. I have taken this matter up and posted some pictures in 'more lbayorkies D1' in the 'restorations documented' folder. I will try to get a fibre washer  to suit from a plumbers merchant. 

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