Author Topic: Douglas Dragonfly Carb Settings & Black Spark Plugs  (Read 3167 times)

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Offline Spash

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  • Location: Worcester UK
Hello all,

I have finally got my wife's Dragonfly on the road and she has been spending the past few months getting used to it however recently we went out and it cut out and I could not get it to start.  I checked the spark plugs and they were as back as coal!!!  I cleaned them up and away she went.  I told my wife to ride with the air inlet lever fully open as I thought that maybe she had been ridding it with it almost closed which I believe would have an influence on the petrol/air mix.  I was told it was running to rich.  When we got back home I checked again and the plugs were black once more.

Could someone tell me the jet sizes for a Dragonfly.  The carb is an Amal 375/004.  I am unsure what jets are in so I will check this over the coming few days.

I am a real novice at these sorts of things so any ideas would be welcome.  She has only rode it for approximately 100 miles in total so I am hoping it is just some simple set up issue.

Regards

Spash

Offline eddie

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Re: Douglas Dragonfly Carb Settings & Black Spark Plugs
« Reply #1 on: 04 Aug 2016 at 14:26 »
Hi Spash,
               The jets for the Dragonfly carb are: main jet 140, needle jet .107, pilot jet 25, and a 3 cutaway slide. These were the standard jets for the fuel available in the mid 50's - I have found on unleaded fuel the Dragonfly runs better and picks up cleaner with a 3 cutaway and 150 main jet, then compensate by dropping the needle to the lowest setting. These settings give slightly richer mixture, so may not be suitable for your bike until you have sorted the problem.
  The fact that your machine is running rich begs the question "Have you fitted a fibre washer under the fitting that takes the fuel banjo on the top of the float chamber?" This fitting should not have a washer, screwing directly onto the top of the float chamber - fitting one will greatly raise the fuel level.
   As your wife is still getting used to the bike, I would expect that she is still only using about half throttle, so the problem probably lies with the slide cutaway or the needle jet/needle assy.
  As you say, the air slide should only be used for starting with a cold engine - once the engine is warm, the air slide should be opened fully.

  Regards,
                Eddie.

Offline Spash

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Re: Douglas Dragonfly Carb Settings & Black Spark Plugs
« Reply #2 on: 05 Aug 2016 at 07:00 »
Hello Eddie,

Thanks for the excellent advise.  I will take a look and see what I find.

Thanks  again.

Spash

 

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