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Dave

2024-06-11, 20:02:05
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Dave

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.

Dave

2024-06-07, 02:13:36

Dave

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

Dave

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


Dave

2024-06-01, 18:33:27

Dave

2024-05-28, 00:09:46
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Ignition timing for 2 3/4 Douglas

Started by Ian, 18 Oct 2004 at 00:51

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Ian

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 ?

Doug

Ian,

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.  

-Doug

Ian

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 !!

Domas

Hello.
Is there a more detailed guide now?

graeme

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

Domas