General => Douglas Motorcycles - General Discussion => Topic started by: wisleon on 13 Mar 2019 at 18:46

Title: Amac carb
Post by: wisleon on 13 Mar 2019 at 18:46
Hello folks;
Am looking for help setting up this Amac carb on a 1913 2 3/4hp machine; fairly new to Douglas and can find nothing online re this design of carb!
Setting correct fuel level and jet adjustment has failed so far.
Any help very welcome. Thanks Leon
Title: Re: Amac carb
Post by: Hutch on 15 Mar 2019 at 01:29
Welcome to the forum Leon! Nice looking Douglas 2 3/4 HP you have.

I have also not found a lot of info. on these circa 1914 AMAC carbies, but some information can be found in the Douglas 2 3/4 HP instruction booklets and in the AMAC Hints and Tips brochures. A copy of these can be found here;

(note:- this is the 1925 version which contains information on the later carburettors used on the 2 3/4HP)

I have attached the AMAC carby pages out of the 1914 Working instructions of the 2 3/4 HP Douglas Motor Cycle. Reproduction copies of this can be obtained from the LDMCC

These carburettors are essentially the standard AMAC carburettor of the day with a heat jacket added to help prevent carburettor icing in certain atmospheric conditions. If your circumstances required this feature, you would need to add a small diameter (copper) pipe from the blanked off fitting on the rear cylinder exhaust pipe of the to the rear hole on the underside of the heat jacket on the carby. These would have had a small clamp on them to clamp the pipe into the fitting. There is then another "mini" exhaust pipe going from the front hole downwards to exhaust the hot gas towards the road. As a lot of 2 3/4 HP's with AMAC heat jacketed carbies have not got the heat jackets connected up it probably is not essential for correct running in most cases?

Your carburettor also has an "aftermarket" adjustable jet needle added to the main jet. This may complicate the tuning procedure until you are familiar with its adjustment - I guess in days gone by people felt the need to fiddle with the adjustment - just like today I suspect!!    :) .


Title: Re: Amac carb
Post by: wisleon on 16 Mar 2019 at 09:18
Hi Ian;
Thanks for the information provided it is extremely useful; particularly the Amac carb "Hints and tips".
Entered the bike for the Pioneer run next weekend so it should now be suitably fettled in good time!!
Much obiged!! Leon