Author Topic: B40 star best set up for wrong carburetor  (Read 161 times)

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B40 star best set up for wrong carburetor
« on: 12 November, 2017, 18:55:53 »
My 1965 B40 has a Amal 627 (428) concentric carb. 20 years ago Dave Smith of BSAOC said its from a Trident but is ok and recommended the set up as:

Main Jet: 140
Pilot jet: 20
Slide 3
Needle position 2
Needle jet .106

( I don't actually know how its set up)

I notice that the concentric that was fitted on some later B40's was a 626. So was Dave Smith right that my 627 as set up above should be fine. ?

I am presuming after 18 years of doing nothing in a garage I'll probably need to check/clean/service it. I did take it apart once but only checked if for crud & cleaned jets ( oh yes then had to emery the flange flat that my make over tightened).

I will see if I can the bike going, but would be useful to know if the 627 should be ok.



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Re: B40 star best set up for wrong carburetor
« Reply #1 on: 12 November, 2017, 19:18:01 »
Your bike would have had a 1 1/16 inch monobloc, about 27 mm bore. The 627 is also 27 mm bore.

Condition is important.

Lots of information on the Amal website including rebuilding the Mk1 concentric, see link;

Also see the tuning guide,

You should find all the information you need and you will be getting it from the manufacturer.