Amal Monobloc Jet Sizing

Joined
Apr 17, 2012
Messages
21
Can anyone tell me what size jets to run in a 63 Atlas with 389 Amal Monobloc carbs when most of the riding will be done between 5 and 9,000 feet above sea level.
Thanks
 
I run the needles on mid notch at sea level on my 63 Atlas. At altitude, i would first try dropping the needles one notch lower than mid level before changing jets.
 
You can lower the needles until the motor coughs when you ride the bike around a twisty road, then raise them one notch. It should clear and run strongly without missing.
 
What numbers are on the monoblocks fitted to your Atlas ?
And what jetting is presently in them.

Bacons book on Nortons lists the jet settings for various years of Atlases.
Anything from 350 to 420 on the mains too.

9000 ft should require a bit less, probably quite a bit less.
You wouldn't be able to take it down to sealevel though ?!
 
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