Wont Start When Hot (Magneto?)

Helpful information and requests for assitance and advice
User avatar
bunners
Member
Posts: 664
Joined: Wed Jan 21, 2009 2:24 pm
Location: HAMPSHIRE UK

Re: Wont Start When Hot (Magneto?)

Post by bunners »

Sorry Russell just trying to help.
If there is life after Death whats the point of dying in the first place.
Groily
Member
Posts: 2151
Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: Wont Start When Hot (Magneto?)

Post by Groily »

Sod's law Russell - there are quite a few 15mm drive end armatures about (pre-'51/52ish?), but most 'off the shelf' swaps will be 18mm that end. Boring out the earlier bodies to take the larger bearing is a rather fiddly job which I haven't much enjoyed when I've had to do it - as it comes with some risk . . . . You're doing the right thing!
User avatar
Joker_Bones
Member
Posts: 539
Joined: Sat Apr 27, 2013 3:51 pm
Location: DORSET UK

Re: Wont Start When Hot (Magneto?)

Post by Joker_Bones »

bunners wrote:Sorry Russell just trying to help.
Bunners.... I wasn't looking for an apology.

I was happy to get the tip on someone local who carries out magneto work. Much preferred to drop the armature off, meet Dave and have a chat. He showed me an old Bosch horseshoe mag (off a vee twin Excelsior) he was restoring and had running on his test rig and some other bits and pieces. I could have stayed and chatted all evening, but although he was friendly and accommodating I didn't want to outstay my welcome :-)

Russell
User avatar
Joker_Bones
Member
Posts: 539
Joined: Sat Apr 27, 2013 3:51 pm
Location: DORSET UK

Re: Wont Start When Hot (Magneto?)

Post by Joker_Bones »

Groily wrote:Sod's law Russell - there are quite a few 15mm drive end armatures about (pre-'51/52ish)
The bike is a '55.... Well the crankcase is stamped G9/55 and the numbered part of the frame is '55 Ajay, but (like many I guess) there seems to be an assortment of parts from different bikes and years.

The magneto is date stamped '51.... Mr. Fisher said that was the last year of the 15mm dia. shafts, relating a story which attributed the increase in dia. to the failure of the smaller ones on some works Triumphs. :)
User avatar
cf160
Posts: 522
Joined: Sun Jul 30, 2006 7:24 am
Location: Ottawa, CANADA
Contact:

Re: Wont Start When Hot (Magneto?)

Post by cf160 »

I realize this thread is over 5 days old now (since last post) BUT if anyone is still looking at this VERY common problem with Lucas Mags, I would like to suggest to anyone who is interested that Lucas recently (1975 or thereabouts) published articles which I found in Christian's Archives which clearly explain that the mags made in the 50's and 60's all fail after 20 years because of the cheap (shellac) insulation used on the windings of the armatures in Mags and some field coils in the "3L" generators. The article describes exactly the symptoms J. Bones describes and which I also experienced with my K2 mag from 1961.
I bit the bullet and sent it to a Mag man in Maine , U.S. who did an armature rewind , condenser replacement. He says he tested it running for two hours . Cost , including parts and labour and shipping, $450. US. A bit pricey ,I thought, but guaranteed for one year.
It's been four years and I haven't tried it yet.
Oh yes, the Lucas article explains why bad windings will work until hot, then NOT work until cool again. I forget the reason.Perhaps a physicist in the club can explain.
David J.Potter
User avatar
Joker_Bones
Member
Posts: 539
Joined: Sat Apr 27, 2013 3:51 pm
Location: DORSET UK

Re: Wont Start When Hot (Magneto?)

Post by Joker_Bones »

It's been a while since I posted this. I got side-tracked.

Mr Fisher said it would be a few weeks to get my mag armature rewound... While waiting I got it into my head it would be a good idea to build myself a new shed (you know... just for bikes and tools, not old tins of paint and gardening stuff) it would only take a couple of weekends.

Yeah right!... Many many weekends later... I finally got around to putting the mag back together and fitting it on the bike (in my new shed I have to add).

Now... she starts cold, warm or hot... just a prod and off she goes!

Thanks to those who helped :)

Russell
Johnobirches
Member
Posts: 155
Joined: Mon Jul 08, 2013 10:19 am
Location: Lancs. UK

Re: Wont Start When Hot (Magneto?)

Post by Johnobirches »

Thanks for posting the update/outcome Russell. Hearing how things ended up is very helpful to those of us with similar symptoms and searching the forum for solutions.

All the best.

John
User avatar
1608
Member
Posts: 2493
Joined: Mon Oct 05, 2009 1:00 am
Location: ESSEX UK

Re: Wont Start When Hot (Magneto?)

Post by 1608 »

Hi Jono. you are aware that that update is 3yrs old :rofl:
Locked