Author Topic: Douglas Dragonfly Parts Wanted - Carburettor intake & Battery box cover  (Read 811 times)

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Offline EnglishAndy

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My father's 1957 Dragonfly has a piece of what seems to be automotive coolant hose, going from the carburettor to the battery box. There is an air filter in the battery box. I want to remove it, as it keeps falling off and looks bloody awful. Does anyone have the small circular plate that attaches with 4 bolts, please? Also, is there supposed to be a flared end to the carburettor inlet, like a bell inlet? If so, I need one of those too, please.


« Last Edit: 05 Feb 2019 at 21:01 by EnglishAndy »

Offline andy1303

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I'm pretty convinced the air filter in the toolbox and the bellmouth inlet were alternative options at purchase.

My bike was the same as your with the filter and for me it was hoover hose making the attachment. i bought an air intake from Hitchcocks, and I can't remember how I got the plate (possibly either through this site or from a LDMCC club member), but if you search the forum I'm sure there will be a post by Eddie advising re-jetting the carb for the increased airflow when you remove the filter.



Offline eddie

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As Andy1303 says - the air filter assembly was an optional extra on the Dragonfly. If you are reverting back to the standard set up, you will need a standard bellmouth for a 375 Monobloc carb, and the blanking plate for the toolbox. I have checked on the size of the plate on my Dragonfly, and it is a 20g flat steel disc 3 5/8" dia - with 4 holes to match those in the toolbox. The standard size of main jet in the Dragonfly carb. was a 140 - reduced to a 130 if an air filter was fitted. This was, of course, when we ran on proper petrol (instead of the dreaded unleaded). Most of us have found that we now need to increase the main jet size by 10 to obtain better and cooler running with the modern fuel. A slightly smaller slide cutaway also helps with getting a clean pickup from tickover. The increase in jet size seems to keep the temperature under control enough that I haven't had  to resort to using fuel additives, or having hardened valve seats fitted. When I did experiment with using Castrol Valvemaster additive, I found the fuel quickly went stale in the tank.


P.S.  If the air filter fitted to your bike is an original, it should have 4 mounting studs around the air pipe (for bolting it to the inside of the front of the toolbox) and therefore, it shouldn't be possible for it to 'fall off'. The carb would originally have had a screwed on adaptor to take a short plain rubber hose.
« Last Edit: 09 Feb 2019 at 10:39 by eddie »