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My Norton/Gold Star

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Cracked the old single into life today. Sounded OK but was running extremely rich. I have an Amal concentric series 2000 carb fitted and I am wondering if the float needle is stuck open. I believe there is a modification where the float is changed to a 'stay-up'. I have no identification numbers on the carb only AMAL MADE IN SPAIN any clues on how to set these carbs up would be helpful.
The timing may not be spot on, maybe slightly retarded but that should be easy to sort out as I have electronic ignition which has a pointless distributor where the mag should go so it is only a twist one way or the other.
Roll-on spring time so I can get the baby out on the road which she hasn't seen for over 40 years!

Morning Oldtimer,

Goldie in a Featherbed has to be up there with the Duke for producing  ;D ;D ;D ;D ;D! It needs to be out and about.

I can provide part numbers etc, but just need to clarify that the carb is an Amal Concentric MKII and if so, what actual size the the bore is? Has the motor been ported and gas flowed or has it a standard  head?

A 'Stay-up' float etc are all available 'off the shelf'.

Here is the link to the Amal MKII 2000 Series home site: MKII-Concentric-series/2000-series

Drop the float bowl and see if it is full of crud. Ruddy ethanol fuel/condensation soon corrodes the aluminium alloy (MKI's are zinc alloy), so keep it drained, unless in use. Be warned that sonic baths don't always cope with the corrosion and the small drillings in the carb body can become blocked, rendering the instrument useless!  :(  I have cleaned carbs using an orbital sander to provide the agitation, but it is a messy and vexing job requiring patience and an air compressor as well!

All the best, Bill

If it hasn't run for 40 years then ethanol is unlikely (not that I subscribe to that theory anyway).

If the float needle was stuck then there's be petrol everywhere......

I would certainly pop the carb off and give it a good clean however.

The carb was stripped down and new jets inserted. As I was unable to assert what number on the jets I required I went for the middle of the choice of three. I still have the original jets but as for identifying them!!!!! or whether they are clear I do not possess a microscope! As for the model number on the carb there aint any just 'Amal Made in Spain.
BILL, without taking the carb off [pain in the arse!] I assume it would be 1.1/2" [38mm] as per the original GP
Regards Mike

Aye Mike,

Jet sizes in the 'Original' GP, probably T3GP are as listed in the Amal parts list:

Main jet: 376/100 - 350
Pilot jet: 376/076 - 25
Needle jet: 316/065 - 109
Needle: Position 3
Throttle valve/slide: 316/4134A cutaways 3 - 8 (Linear steps of 1/16", so 3 = 3/16" height of cutaway from base of slide to highest point of cutaway.)

So, having done a search, this link to an Amal MKII Concentric tuning guide looks promising: Amal_MKII_fitting_tuning_instructions

And then I found this post on the BritBike Forum that appears to be a wee bit of 'star dust' to make your eyes twinkle  ;)  : Proper_settings_for_Gold_Star_carburettors

The latter will answer the questions. For reading the jet numbers/ needle numbers, I use a Watchmakers loop or a stand magnifier for reading maps/books.

If you would PM me your email address, I will send a scan of a numbered, exploded diagram of the Amal MKII 2000 series carb and the parts list from the Amal catalogue.

Hope this helps.

My regards, Bill


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