Author Topic: Newbie looking for sparks  (Read 501 times)

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Offline Sams Dad

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Newbie looking for sparks
« on: 14 Jul 2021 at 21:04 »
Hi All,  I am new to Douglas and the forum. I have just got a Dragonfly and no spark,   but I am not sure where to start. Wiring seems roughly ok as lights and horn work on the ignition and power to low tension as it sparks on the casing if struck along it. Where should i be looking next ?  Distributor cap looks ok as do ht leads.  What is points gap ?  How to test condenser and how do the wires on l/t side go on the mag as it was all loose.

Offline patrickwhitty

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Newbie looking for sparks
« Reply #1 on: 15 Jul 2021 at 06:32 »
My Dragonfly lost its spark a couple of weeks ago, it was getting side tracked in the distributor casing. I tested it with one of those circuit testing things like a screwdriver with a light in the handle. There was power getting into the distributor but it escaped past the thin slither of plastic between the points spring and the case. I improved it with a piece cut from the lid of a margarine tub. Next time I am working on the distributor I'll glue it to the inside of the casing, there are too many loose bits needing to be connected and not enough space to work.
So far as I know the most convenient way to test a condenser is to replace it with a new one, hoping that isn't faulty.
Good luck with finding your sparks. I hope you are soon out on the Dragonfly.
Patrick

Offline eddie

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Re: Newbie looking for sparks
« Reply #2 on: 15 Jul 2021 at 07:00 »
Firstly, assuming you still have the original Miller distributor, turn the engine until the points are open, remove the LT wire from the distributor, and put a low wattage bulb in circuit and check whether it lights when the ignition is turned on. If it does, there is a short circuit in the LT side of the distributor. The most likely culprit is that the spring blade on the points is shorting to the distributor body. Inside the body, there should be a thin fibre strip separating the spring blade from the body. Also, the hole for the terminal bolt should have 3 small fibre washers in it preventing the bolt from touching the body (these are very fragile and are often in a state of collapse). Finally there should be another fibre washer on the outside of the body, a plain washer and nut, then another washer and nut to secure the LT connection.
   If all is OK with the LT side, check the HT side (the distributor cap). Undo the 2 screws that retain the clamp that secures the HT leads. Check very carefully for any signs of the spark tracking across the top of the cap (lead to screw to lead, in any direction). Any sign of tracking will cause the spark to travel to the wrong cylinder - the line of least resistance is always to the cylinder that is NOT under compression. If there is any signs of tracking, scrape away all the charred Bakelite and fill the groove with 24 hour Araldite to prevent further tracking. Also, check that the engine is timed on the correct cylinder (with the valves rocking - going from exhaust to inlet - on the LH cylinder - the RH cylinder should be firing) - quite a few Dragonflies are timed so that the HT leads cross (under the cover).

  If you suspect the condenser is faulty, replace it with one for something like a Morris Minor - ignition condensers are not particularly voltage sensitive, so one intended for 12 volt will work on a 6 volt system. My bike has been running on a Morris Minor condenser for the last 20 years - I have, however, made a small alteration in that my condenser is mounted alongside the ignition coil and connected to the other end of the LT lead (I know they should be mounted as close as possible to the points but they definately don't like being cooked under that cast alloy distributor cover!).

   Good luck,
                    Regards,
                                  Eddie.
« Last Edit: 15 Jul 2021 at 08:29 by eddie »

Offline Sams Dad

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Re: Newbie looking for sparks
« Reply #3 on: 19 Jul 2021 at 00:33 »
Thanks very much for your help chaps. It appears the L/t was wired right and was not shorting bon the dizzy body. The points were gapped too wide and i have reset them at 12 thou and gave them  a clean then low and behold sparks at the points. Reattached dizzy cap and sparky plugs too!  Auxiliary tank on with a bit of juice in and a little tickle , set the choke and kicked with a little throttle then fired up and ran!  Had a little ride across our yard and the clutch is dragging,   but the gears selected ok and the brakes work after a fashion.  A lot of stuff seems loose on it but it lives yay!   Thanks for all your help.  Greatly appreciated. I didn't even need to clean out the carb.  I need to set the tappets /valve clearances I think and set up the carb and timing plus check everything is tight,   particularly the front end which seems all very vague. Otherwise seems a good little runner.  I assume there is an auto advance /retard on them as i can't see a lever for manual?

Offline patrickwhitty

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Re: Newbie looking for sparks
« Reply #4 on: 19 Jul 2021 at 06:46 »
Congratulations! Yes, there is an automatic advance below the baseplate on the Miller distributor. Dragonfly brakes do work after a fashion but adjustment may make some improvement. You may find the front end feels less vague at road speed rather than crossing the yard speed, unless you have a very extensive yard.
Patrick