Author Topic: RGS carb differences  (Read 88 times)

Offline a101960

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  • BSA RGS BSA C12
RGS carb differences
« on: 26.10. 2020 10:57 »
Does anyone know why the RGS according to "BSA twin restoration" book  has three different carb specifications? and does it make any difference?

1962-63      389/80 size 1 - 5/32    main jet 420   pilot 25  slide 3 needle position 2    jet .106

Then for 1962

389/81 size is now 1 - 3/16 and main jet is specified as 440 pilot 30 and slide 4 jet needle is now .107

1963

389/94 size is back to 1 - 1 5/32 main jet 310 pilot back to 25 slide back to 3 but needle jet .104

The owners RGS owners hand book spec is listed as 389/80 size 1 - 5/32    main jet 420   pilot 25  slide 3 needle position 2    jet .106

There must be a reason for the alternatives but in Bacons book there is no explanation.

Offline JulianS

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Re: RGS carb differences
« Reply #1 on: 26.10. 2020 13:12 »
Some information on the 1963 A10 Super Rocket, RGS, RGS Scrambler carbs on parts bulletin N8 and also the Gold Star twin supplementary list from February 1963.

These give 389/94 as used on the 1963 USA West Coast Super Rocket and RGS Gold Star twin and 389/81 used on the 1963 East and West Coast scrambler models.

This seems to coincide with the introduction of the 9:1 pistons.

As usual no explanation given in the bulletin.