1963 T90 Carburettor

spanman

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1963 T90
Instruction Manual No.4 for my 1963 T90 specifies the carburettor as an Amal 376/300. Whilst I have an Amal carb, the body is marked RB 928/8. Presumably this means it is a Mark 1 Concentric 900 series with a 28 mm bore. Does anyone know whether this was a later specification or has it been changed by a previous owner for some reason?
 
Instruction Manual No.4 for my 1963 T90 specifies the carburettor as an Amal 376/300. Whilst I have an Amal carb, the body is marked RB 928/8. Presumably this means it is a Mark 1 Concentric 900 series with a 28 mm bore.
Yes. The "R" says the air screw and tickler should be on the right hand side of the body when the carb is mounted on the engine. Not sure what the "B" means, Amal might be able to tell you.

Does anyone know whether this was a later specification
It was not, Concentric on a Tiger 90 was a 624 (600 series body with a 24 mm bore).

The only Triumph "C range" (350 and 500 unit construction engines) fitted with a 928 was the 73/74 TR5T 500, the only other Triumph range fitted with 928 were 68 and later 250 singles; all had numbers after the "/" higher than 8 so 928/8 was likely new on a BSA.

376 Monoblocs are available new; /300 is not listed but, based on the 24 mm Concentric, I suspect it was 15/16" bore, Amal will confirm or correct.
 
Thanks Rudie, I'm now getting into the detail of this with great interest. A bit more research revealed some brilliant information online at Notes On Rebuilding the Amal Mark 1 Concentric Carburetter - The AMAL Carburetter Company. This stated that the 'B' refers to an upgraded needle and needle jet. I've now ordered a gasket set (for about a fiver) from Burlen together together with a Catalogue (free of charge) with the intention of cleaning and rebuilding my Amal 928 as the next step.
 
get a new needle jet, whether you think you need one or not.
 
Instruction Manual No.4 for my 1963 T90 specifies the carburettor as an Amal 376/300.
intention of cleaning and rebuilding my Amal 928
:confused: 376/300 was 15/16" bore. 928 has a bore area over 38% greater. Attempting to use the 928, you will have great difficulty getting your T90 to run correctly (at all?) especially at low rpm.
 
that is a pretty large carburetter for that machine, but ive fitted very over-large carbs before and had them work. larger motors to start with, though. was this carburetter on the machine and functioning, or did it arrive as a basket case?

there is an excellent source of non-factory information about the monoblocs and concenetrics available for not much money here:


the tuning sections of these booklets are excellent.
 
This carb (the RB 928/8) was fitted to the bike when I bought it about 5 yrs ago. The engine started easily, ran perfectly and ticked over without missing a beat. The only reason for removing it was to make sure there was no ethanol damage, which there wasn't. It was then that I started looking at specifications.
 
if it works, run it. engines are much more forgiving of carburetor size than we like to say.

i run 34mm and 35mm japanese carbs on 650s (stock is 30mm) and have no issues. i routinely run 30mm concentrics on machines designed for 28 and have no issues there either.
 
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since it isnt the original carburetter, tho, you might benefit from checking thst its jetted as well as it could be. thats not hard to do.

needle jets wear out quickly in these carbs, and are often junk after about 10000 miles and due for replacement.

what is the slide number, needle jet number, and main jet number that are in the carb now, as you are running it?
 
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