Douglas - For Sale Items

Douglas 1913 Model P motorcycle

Douglas - Wanted Items

Douglas 1915 3 Spd-Gearbox and Clutch

Quick Comments

Reminders, links to interesting topics, bump your own topic, quick comments or any short message of interest to members. Try it out!
Please note - 500 character current limit


2024-06-11, 20:02:05
Have you tried the new Drafts feature yet? I just lost a long message today and learned my lesson. It is a good idea to save a draft of any long post you are writing. You can then just keep writing and keep saving a draft, knowing you have a backup if there is a glitch. The draft is automatically deleted when you post the message.


2024-06-08, 18:30:04
For Sale
xman has two very nice 1950's machines available - a green 1950 mk4 and black 1951 mk5 - both in good condition and running well.


2024-06-07, 02:13:36


2024-06-03, 08:23:05
For Sale
Duncan has just listed his green and cream 1957 Dragonfly for sale with spares and documents.


2024-06-02, 08:34:05
Parts avalable
alistair still has parts available - barrels, carburettor, castings - see all listings.


2024-06-01, 18:33:27


2024-05-28, 00:09:46
Welcome to the new site!
Recommended viewing for a fast start...
 - Quick Tour of the Front Page
 - Quick Tour of the new Attachments
Learn all about attaching photos in the User Guide. Any problems with anything please Contact us     Faulty links fixed - 01June2024

Ignition timing for 2 3/4 Douglas

Started by Ian, 18 Oct 2004 at 00:51

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.


I am concerned that my 2 3/4 Douglas is running too hot and want to check the timing. The manual has a process for setting but does not mention what degrees BTDC it should be set at. Anyone got that info ?



All the 2-3/4hp instruction I have seen have the same non-engineering method of setting the ignition timing.  For those not familiar I paraphrase it here:

When the exhaust valve is just closing, the opposite cylinder is at its firing point.  Set the advance/retard control lever midway between full retard and full advance.  Turn the magneto so that the points are about to separate (the fiber shoe is just touching the cam.)  The magneto can then be installed, the gears meshed, and then secured.  

Obviously the ignition timing is not very critical!  Make sure if you are timing the front cylinder, you are not firing the rear plug.  Else you will find the engine will be very, very cold!   :D  

The previous depends on the exhaust timing being correct.  The exhaust should close 10º after top dead center, or less precisely, when the piston has descended 1/16".  

If you do not like that method, you could probably use the ignition timing for the 350cc EW model introduced in 1925, which was just an up rated 2-3/4hp.  The service book for the 350cc EW says to set full advance for 50º before top dead center.  



Thanks Doug. I will see how different the two methods are !! I can't see how I can get anywhere near what would be a normal advance using the original method - half travel of the lever from 10 ATDC !!


Is there a more detailed guide now?


The 2 3/4 is essentially a veteran design, and the rule-of-thumb for veterans is to set the ignition for around 35 - 40 degrees BTDC at full advance. I think the 50 degrees mentioned above in relation to an EW 350 would be a bit exciting on a 2 3/4!
With the outside flywheel on the Douglas it is very easy to set up a degree disc to do this with a good deal of accuracy.

Cheers, Graeme