General => Douglas Motorcycles - General Discussion => Topic started by: Alex Hall on 12 Jul 2008 at 10:14

Title: New Caretaker
Post by: Alex Hall on 12 Jul 2008 at 10:14
Hi, I m the new caretaker of 2 Douglas's. A MK3 Sports and Mk 4 Sports. I m in Malta where I found the bikes. Both in good shape, Mk 4 can easily be concourse, whilst Mk 3 is unrestored and showing slight signs of aging  but otherwise in good nick. Trying to get the Mk 3 up and running, cleaned fuel systems and found that the fuel taps would need attention but other than that and the fuel pipes being brittle nothing seem damaged. So yesterday tried firing up. Irregular spark on one cylinder, eventually found to be HT lead or brush holder. Still the problem with one cylinder firing whilst the other is non cooperative. Was about to check points but then realised that the original owners handbook or spares book don t include Lucas Magdyno. Can any one advise on how to go about adjusting after cleaning the points please? Is the Lucan handbook on the Magdyno available to buy as a copy? Alex
Title: Re: New Caretaker
Post by: Doug on 12 Jul 2008 at 15:43

Lucas put out several workshop instructions of a few pages on the various electrical components. I will email you the pertinent ones.

Also I have come across Magdyno point housings where the mounting spigot, bearing bore, and cam ring bore were not machined concentric. Look into this if you find the point gap significantly different for each 'side'. This causes the points to open at something other than 180 degrees apart, and can be a persistent source of uneven running. You can replace the end housing for a better one, have a machine shop rectify yours, or modify the cam ring to compensate.

Title: Re: New Caretaker
Post by: Alex Hall on 12 Jul 2008 at 18:28

Thank you very much. Will begin looking into points housing and see how it looks. I suppose the housing comes out as one piece with the whole magdyno unit not on its own? Will keep you posted.
Title: Re: New Caretaker
Post by: eddie on 12 Jul 2008 at 21:01
         A common fault with Lucas magdynos is that the paper cage that surrounds (and insulates) the bearings sometimes disintegrates, allowing the armature to shift sideways, thus giving wildly varying points gaps. This usually results in the symptoms you are experiencing. Try gripping the points centre bolt and check for any movement either axially or radially - if any movement is detected, the bearing cage has probably disintegrated, in which case the magdyno should be removed - quite a simple task as on Mark series machines the timing gear comes through the hole in the back of the timing chest, and so does not have to be disturbed. Working on the points end of the mag is much simpler with the unit removed from the engine. Firstly, remove the centre bolt that retains the points assy - then lightly lever the points assy until it frees from the taper. remove the 4 screws that retain the back plate. This should come away complete with a couple of shims and the outer track of the tail bearing. The loose outer track can be rectified by cutting out a new cage from a suitable thickness card. Improved support for the bearing can be gained  by 'Aralditing' the bearing and cage into the backplate. Do not try to make a metal sleeve as this will allow the armature to 'earth' though the bearings - causing early bearing failure. When repaired, the magdyno will of course have to be timed when refitted.
             Good luck with the repairs,