Author Topic: Carb confusion  (Read 1647 times)

Offline ChasF

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Carb confusion
« on: 04.02. 2018 15:04 »
When I first had my Golden Flash back in 1975 I think it was fitted  with a 376 1 1/16” carb. I have since acquired a 389/6 1 1/16”, a 389/1  1 1/8” and a mk1 concentric 1 3/16”. All have been on the bike a one time or another and all worked well enough except the concentric which made the bike hard to start but it ran fine once started.

I was thinking I’d fit a new carb which according to the Amal site is a 276 1 1/16” for my 1954 bike but then I noticed that the 60/61 Golden Flash was fitted with a 389/45 1 1/8” unit which is about £100 less expensive than the 276.

I notice that the inlet is 1 1/16” but easily taken out another 1/16”. Also the 389/1 in my collection is in good nick and with a few new parts would be serviceable.

First thing I’d like to know about is what do the Amal suffixes relate to? Also why is the 276 so much more money and is there any reason why I shouldn’t fit the later spec 389 carb ?

Exiled Brit living in the Dordogne

Online JulianS

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Re: Carb confusion
« Reply #1 on: 04.02. 2018 15:44 »
The Amal suffix relates to the original build specification - the bore, jets, slide etc. It will relate to set up for a specific bike but after all those years could have had jets etc changed for a different bike.


Offline RogerSB

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Re: Carb confusion
« Reply #2 on: 04.02. 2018 19:52 »
My 1960 Golden Flash carburettor spec. if it's any help to you.

Amal Monobloc 389/45 (pt no 42-0173)
Bore 1 1/8”
Main Jet: 250
Pilot Jet: 30
Throttle Slide 389/3½
Needle Jet: .106
Needle: D
Needle Position (from top): 3

1960 Golden Flash

beezermacc

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Re: Carb confusion
« Reply #3 on: 04.02. 2018 20:11 »
The 276 was the pre '54 carb with the separate float bowl as used on the plungers.

Offline KiwiGF

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Re: Carb confusion
« Reply #4 on: 04.02. 2018 20:16 »
When I first had my Golden Flash back in 1975 I think it was fitted  with a 376 1 1/16” carb. I have since acquired a 389/6 1 1/16”, a 389/1  1 1/8” and a mk1 concentric 1 3/16”. All have been on the bike a one time or another and all worked well enough except the concentric which made the bike hard to start but it ran fine once started.

I was thinking I’d fit a new carb which according to the Amal site is a 276 1 1/16” for my 1954 bike but then I noticed that the 60/61 Golden Flash was fitted with a 389/45 1 1/8” unit which is about £100 less expensive than the 276.

I notice that the inlet is 1 1/16” but easily taken out another 1/16”. Also the 389/1 in my collection is in good nick and with a few new parts would be serviceable.

First thing I’d like to know about is what do the Amal suffixes relate to? Also why is the 276 so much more money and is there any reason why I shouldn’t fit the later spec 389 carb ?

If you are not bothered about originality I’d go for a new concentric in 28mm, I think these are cheaper than monoblocs? And arguably a better design  *fight* and use the same jet sizes as the monoblocs (I’m fairly sure on that).

The 389 you have would be ok if in good nick and your cheapest option depending on what’s wrong with it, I had a 389 on my 56 A10 but with a fairly worn slide, so I bought a new 376 in the correct size of 1 1/16 which made it idle MUCH better and improved fuel consumption thus paying for itself, but any new carb would have done the same most likely.
New Zealand

1956 A10 Golden Flash  (1st finished project)
1949 B31 rigid “400cc”  (2nd finished project)
1968 B44 Victor Special (3rd finished project)
2001 GL1800 Goldwing, well, the wife likes it
2009 KTM 990 Adventure, cos it’s 100% nuts

Offline trevinoz

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Re: Carb confusion
« Reply #5 on: 04.02. 2018 20:19 »
I think that you will find that the 389/1 is 1-5/32".

Offline ChasF

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Re: Carb confusion
« Reply #6 on: 05.02. 2018 17:42 »
I think that you will find that the 389/1 is 1-5/32".

So it is, do you think the extra 1/32” would make much difference - I remember that the 30mm concentric made the bike difficult to start and I always assumed it was because of the diameter.

Exiled Brit living in the Dordogne

Online Triton Thrasher

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Re: Carb confusion
« Reply #7 on: 05.02. 2018 18:18 »
Going bigger than standard on the carb is an experiment.

Is that what you want?

Offline ChasF

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Re: Carb confusion
« Reply #8 on: 11.02. 2018 17:46 »
Thanks for the comments and advice. As the aim of my refurb. Is to make the bike easy to live with  I’m not aiming for any gain in performance or difficult starting as experienced when the 30 mm concentric was fitted (dodgy knees, these days!). So I’ll go for a new 389/45.

Exiled Brit living in the Dordogne

Online berger

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Re: Carb confusion
« Reply #9 on: 11.02. 2018 18:10 »
when I got my beezer in the 70s[ a7ss engine]some lunatic had put a 30mm concentric on it. it sutted plugs ate petrol and was a very unhappy bunny, my mate gave me a monoblock and she became a happy bunny again. last year she got a mikuni , I didnt really want to but fighting a 60 year old carb to get her running from tickover all through the revs became too frustrating. she is now a really really happy bunny