Author Topic: Jet on Amal 389 to BSA Golden Flash  (Read 318 times)

Offline GFlash

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Jet on Amal 389 to BSA Golden Flash
« on: 19.05. 2018 15:45 »
Hi
Has a Golden Flash from 1954 with 357 cam and open silencer.
Has mounted an Amal 389, which sizes of main jet, needle jet and pilot jet should be appropriate?

Regards
Robert

Offline RogerSB

  • 1960 Golden Flash, Plymouth, Devon, England
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Re: Jet on Amal 389 to BSA Golden Flash
« Reply #1 on: 19.05. 2018 17:36 »
Hi Robert,

As far as I know 1950 - 54 GF originally had an Amal Monobloc 276.

My 1960 GF has a 389 with 1 1/8" choke, 250 main jet, 30 pilot jet, 3 1/2" throttle slide, 0.106 Needle jet, No3 (from top) needle position.

1960 Golden Flash

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Re: Jet on Amal 389 to BSA Golden Flash
« Reply #2 on: 19.05. 2018 21:53 »
G'day Robert.
You don't say what size 389 you have or air filter.
With a straight through pipe and 357 cam and a choke size of 1 1/8" I'd start with a 300 main, the rest as per Rogers settings or just a tad richer and go from there.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
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Offline GFlash

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Re: Jet on Amal 389 to BSA Golden Flash
« Reply #3 on: 22.05. 2018 21:13 »
Thanks for reply.
I have air filter.
Measured and saw that the carburettor is 1 1/8" and the intake is 1 1/16" understand that it is not good?

Regards
Robert

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Re: Jet on Amal 389 to BSA Golden Flash
« Reply #4 on: 22.05. 2018 21:27 »
G'day Robert.
A step like that 1/32" isn't great but it's not too bad. you could use a thick insulating gasket to blend the two together. http://amalcarb.co.uk/phenolic-spacer-26mm.html
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline Scott and Jay

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Re: Jet on Amal 389 to BSA Golden Flash
« Reply #5 on: 22.05. 2018 21:34 »
Yes, the bore on the intake manifold needs to be increased to 1 1/6 and matched to the carb - if you want to keep that carb. I got a new Premier Amal 389 carb for my 1958 Golden Flash. It as 1 5/32 bore. I got the intake bored out to match this. With an air cleaner but not-too -restrictive Emgo universal mufflers - I had to go up to a 310 main jet. It runs really nicely at that.