Author Topic: Dragonfly misfire  (Read 4591 times)

0 Members and 1 Guest are viewing this topic.

Offline Les Mills

  • Full Member
  • **
  • Join Date: Jul 2011
  • Posts: 32
  • Location: Bexhill on Sea
Dragonfly misfire
« on: 11 Jul 2011 at 18:35 »
Hello,
A dragonfly last taxed 1999 found me.  It had been restored just before that date.  I have had the coil and capacitor tested and were fine both plugs give an amazing spark (compared to a Magdyno).
It started easily and ticked over nicely, on riding it misfired from the word go, it got progressively worse and then went onto one cylinder.  Should I look at the distributor? never had one before, or maybe a valve is on the way out.  If it is the distributor anyone know where to get parts please.
             Regards,  Les

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1438
  • Location: Hampshire, UK
Re: Dragonfly misfire
« Reply #1 on: 11 Jul 2011 at 19:34 »
Les,
       From these symptoms, it seems that you may have problems with tracking across the distributor cap. It is quite a common problem with the Miller distributor. You will find there is a clamping plate that retains the HT leads to the top of the cap. Often the spark jumps from the centre lead to one of the securing screws and then to the wrong spark plug lead (the spark always finds the easiest route to earth - and that is through the plug that isn't under compression!). Look carefully for any signs of tracking on the mating surfaces of the plate and cap, and then scrape away the offending area until you are down to clean material, then coat the surface with petroleum jelly (Vaseline). This should cure the problem of the engine going on to one cylinder. If a misfire still occurs, try mounting the condenser on the side of the coil - it will be happier in the cool air rather than cooking under the engine cover. Of course, the body of the condenser will have to be earthed, and the 'live' side connected to the wire from the coil to the distributor.
        I had the same problem with my Dragonfly in the 80's - moving the condenser cured the misfire - and it's still performing well!.
       The Miller electrics are the Dragonfly's Achilles heel - especially now that new spares are so hard to find.

       Eddie.

Offline podge

  • Full Member
  • **
  • Join Date: Jun 2008
  • Posts: 65
  • Location: surrey, england
Re: Dragonfly misfire
« Reply #2 on: 12 Jul 2011 at 10:43 »
Hi Les

I had the same problem on my Dragonfly but cured it by using a Boyer Bransden electronic igniton unit with their twin coil and just using the Dragonfly contact breaker. I had to make a heat sink out of sheet aluminium for the twin coil which fitted neatly under the tank.

Regards and Good Luck

Paul

Offline Les Mills

  • Full Member
  • **
  • Join Date: Jul 2011
  • Posts: 32
  • Location: Bexhill on Sea
Re: Dragonfly misfire
« Reply #3 on: 12 Jul 2011 at 18:04 »
Hi Paul,
               It is running OK now so will leave alone, however I do like modern electrics.  Do you know of any system that does away with the points?  How about a 12v generator, has anyone done that do you know.
               Thanks for replying.
                                                 Regards,  Les

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1438
  • Location: Hampshire, UK
Re: Dragonfly misfire
« Reply #4 on: 12 Jul 2011 at 18:31 »
Hi Les,
            You can convert to 12 volt using the original generator. I have a Special that uses the standard Miller generator wired to give 12 volt and incorporating a Zener diode to dump any excess voltage to earth. Although only rated at 60 watt, when set up for 12 volt, it gives in excess of 8 amps at 12 volt (96 watts). Of course, when operating like this, the generator is giving full output, so needs more power to drive it - not good when you have a Dragonfly with just 18 BHP!
     To get 12 volts, firstly replace the original rectifier with a modern solid state unit. The generator lead that went direct to the old rectifier should be connected to one side of the new unit. The other 2 generator leads that went to the lighting/ignition switch should be joined together and connected to the other side of the rectifier. The Zener diode should then be wired into the output side of the rectifier (to control the maximum voltage).

               Regards,
                         Eddie.

Offline Les Mills

  • Full Member
  • **
  • Join Date: Jul 2011
  • Posts: 32
  • Location: Bexhill on Sea
Re: Dragonfly generator
« Reply #5 on: 13 Jul 2011 at 10:21 »
Hi Eddie,
                  Many thanks for the info. I will store that away until needed or fancied.  A previous owner has fitted a Solid state rectifier which must be an improvement.  I now look forward to getting to know the machine.
                                                   Regards,
                                                                     Les

Offline podge

  • Full Member
  • **
  • Join Date: Jun 2008
  • Posts: 65
  • Location: surrey, england
Re: Dragonfly misfire
« Reply #6 on: 13 Jul 2011 at 14:45 »
Hi Les

I converted my Dragonfly to 12 volts in 2004 as per Eddie's note - no problem encountered. I found the Dragonfly too heavy so sold it last year and replaced it with a Mark 5. As far as points are concerned it is worth having a talk  with Boyer Bransden. I have a Norton Jubilee which 11 years ago was suffering ignition problems with dodgy Wipac points - always going out of adjustment. I converted it to 12 volts and Boyer Bransden supplied me with an inductive system - magnet and two pick up coils - which was a direct mechanical replacement for the Wipsc bits. Used with their electronic box and the existing 6 volt ignition coils wired in series and with a 1/2 ohm ballast resistor no problems - starts first prod!

Regards

Paul

Offline Neil Warner

  • Full Member
  • **
  • Join Date: Jul 2011
  • Posts: 33
  • Location: Billinge Lancashire
Re: Dragonfly misfire
« Reply #7 on: 23 Jul 2011 at 13:44 »
Hi Les,
I have just become the proud owner of a dragonfly with a miss fire. I have cleaned the points, changed the plugs, the coils have been replaced with two coils working as a wasted spark system not using the rotor arm or distributor cap. It worked fine for about 5 miles and then went onto 1 cylinder. I have been investigating using a crankshaft positioning sensor and making an electronic system but my electronic knowledge is limited and would need some help. the boyer system looks as if it is the way to go. Also Moto Guzi points from a Nuvo Falconi seems that the moving contact will fit and the other can be adapted with the aid of a Dremel a and a file. 

Regards Neil