Author Topic: Magneto Seized advance/retard  (Read 432 times)

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Offline Peter Burgess

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Magneto Seized advance/retard
« on: 04 Jun 2019 at 14:52 »
HI,
I've just bought my first Douglas, a mark 5.
It had been standing for many years.
I've got the bike running, but there is no movement of the cam ring.
The cable is not seized as I can move the outer cable when the lever is slack.
I have never dealt with a magneto before.
I've applied "Plus Gas" several times to the edge of the cam ring & given the lever some welly, but to no avail!
Any suggestions most welcome.
Regards,
Peter.

Offline eddie

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Re: Magneto Seized advance/retard
« Reply #1 on: 04 Jun 2019 at 18:34 »
Peter,
          The cam ring may not be seized - if the advance/retard cable is on the long side, it is possible to fit the cam ring with the cable end fitting out of the operating slot.

   First, you need to remove the points cover and undo the centre screw retaining the points plate, then with a screwdriver, prize the cam ring out of it's housing. You will then see that the advance/retard cable has an end fitting with a shallow head that locates in a slot on the outside of the cam ring. Operate the advance/retard lever until the fitting at the mag end is in mid position, then refit the cam ring so that the slot picks up the end fitting. Make sure the cam moves as you operate the advance/retard, then refit the points assembly and cover. Finally, re-adjust the cable so that there is minimal free play.

  If the cam is seized, remove the points cover and gently warm the end of the mag with a hot air gun - the zinc based end plate on the mag should expand enough to get the cam moving and allow some thin oil (3 in 1) to penetrate between the cam ring and it's housing.

Hope this helps,
                          Regards,
                                        Eddie

Offline Peter Burgess

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Re: Magneto Seized advance/retard
« Reply #2 on: 04 Jun 2019 at 21:13 »
That's very helpful Eddie, thank you.
I need to find information on magnetos & a schematic diagram to give me more confidence in tackling it.
Kind regards,
Peter.

Offline isettaman

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Re: Magneto Seized advance/retard
« Reply #3 on: 04 Jun 2019 at 23:43 »
Peter
There's five pages with photographs in Neville Heath's Spannerama book about servicing and restoring magnetos - well worth the 7
Regards
Dave

Offline Peter Burgess

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Re: Magneto Seized advance/retard
« Reply #4 on: 05 Jun 2019 at 17:11 »
Well, I took it apart & removed the cam ring.
I oiled the outside & greased the inside & made sure it was moving ok via the lever & all seemed good.
However, operating it a few times on a short run reproduced the problem.
Closer inspection showed that plenty of nipple was showing at retard on the cam ring, but when raised, much less was protruding!
Probably wear of the nipple & housing.
I've rotated the handlebar nipple by 180 degrees to present the other side of the nipple at the magneto end & it looks better.
Initial trials are encouraging, but I'll try it more tomorrow.
Thanks for help & advise.
I've ordered manuals & parts list from the club.

 

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