Author Topic: starting my Fly  (Read 1184 times)

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Offline Sgtbiro

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starting my Fly
« on: 24 Mar 2021 at 19:03 »
Hi all i am looking for help to get my Fly running i have set up the timing as described to me in a previous post.
the engine fires up and runs for about three or four seconds then dies on me.
i have tried altering the carb but with no luck, any ideas.

Cheers Kevin.. 

Offline kncken

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Re: starting my Fly
« Reply #1 on: 26 Mar 2021 at 17:08 »
Hi Kevin.I got mine back on the road a few years back.and had no end of mysterious conkings-out,and in spite of having a small in-line petrol filter,that ain't no use if the tap itself has no filter on it! The orifice into the tap kept getting covered. Just fitting a replacement tap with a nice tall gauze on top cured everything.Just something for you to check! Good luck.

Offline EW-Ron

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Re: starting my Fly
« Reply #2 on: 26 Mar 2021 at 22:50 »
I'm not sure what carb(s) your 'Fly' will have on it, but a quick-n-dirty test of the
fuel flow situation is try and tickle the carbs when it does start up.
Help from a passing octopus may assist here ...
If it keeps running with some tickling, then you need to look into the fuel supply/float level/fuel needle side of things

Also, do these carb(s) have any choke capabilities ?
Cold engines generally need some choke to assist in the running process.
Pulling on some choke - if you can - may assist in this process.

Some Amal carbs are rather well known for their eagerness to block up the idle jet passages,
and this means when it does start up its running solely on the needle jet.
Which can be pretty rough.
Cleaning the idle passages is somewhat hit-n-miss, it often takes a number of goes to actually get them clear and clean.
This is when it suddenly starts and runs and idles smoothly ...

Tipping/draining the fuel out of the float chambers into a clean bowl and examining for unwanted extras can sometimes reveal
the fuel is not nearly as clean as you may wish .
Having clean fuel delivered out of the tank is a fundamental requirement - any traces of rust or debris is the enemy here !

Whitish corrosion in the floatchamber(s) anywhere is a sign that moisture has been at work,
and likewise this requires every trace of this be removed, or the fuel flow may be hindered.
« Last Edit: 27 Mar 2021 at 03:01 by EW-Ron »

Offline Sgtbiro

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Re: starting my Fly
« Reply #3 on: 28 Mar 2021 at 15:26 »
Hi all can anyone tell me what slot should I be using out of the three on top of the main needle of my carburettor .
If itís in the wrong slot could this be what is preventing my bike from running.

Cheers Kevin

Offline eddie

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Re: starting my Fly
« Reply #4 on: 28 Mar 2021 at 17:42 »
          The original spec for Monobloc carb on a Dragonfly was:  Main Jet 130, needle 3rd notch, pilot jet 30, needle jet .1065, throttle valve 3Ĺ cutaway. Those were the settings for the fuel available in the mid 50's - our modern unleaded rubbish usually gives better results with an increase of 10 on the main jet, and a 3 cutaway on the slide. You could also try a slightly richer slow running mixture.
   The fact that your engine starts but then dies, suggests there may be an air leak on the inlet manifold - possibly on the inlet tubes if they have been re-chromed (the polishing will have reduced the diameter of the tubes). Try applying a bead of silicon rubber around the tubes where they enter the end fittings (leave it to cure for 12 hours before starting the engine) - if that identifies where the leak is occurring, you could try fitting some 'O' rings with a slightly slightly fatter section.