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There has been requests lately on the board for more tech stuff.
Well here'some;

I was checking my LUCAS magneto after reassembly
today, so I took a few pics.

This is the type of mag. you'll find on
most pre-unit BSA's and Triumphs
(if it hasn'tbeen replaced with something less dreadfull)

PART 1 :

OK so you want to check your Lucas on that
non-running 'unfinished project' you just bought?

Here goes:

Remove right side outside cover.
Loosen this nut on the centrifugal timing advancer.
(it does not come off, but comes off together with the advancer)



Remove two nuts and funny-looking-long-thing
that attaches the mag to the engine



Check the plug-wires at the end that goes into the mag



...and remove sparkplug-cap and make sure you have
a good connection
(maybe you'll want to cut of a bit and re-atttach)



Remove the two high-tension pick-ups from the mag
and see if you have sufficient brush left, and they move freely



While hey are off; check that the slip-ring (gold-shiny thingy)
is clean.
If not; clean with a plastic/wooden stick wrapped with a
piece of gasoline-soaked rag.
NO metal rod; if your mag works well,
and you turn it, you'll have one hell of a electric chock

 

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Discussion Starter · #2 · (Edited)
When inserting the brushes; you may have to do
it upwards from below, (turning the mag)
so the brush and spring doesn't fall off, and into the mag



Remove earthing brush by unscrewing this



Check that theres enough brush left



Check cam-ring for surface scratches etc. Polish if necessary



Check the thingy that 'rides' the cam. Polish if necessary



Check the brush on the BACK of the contact breaker-assembly
(out of focus, in the back)



Re-install assembly.
Note that there's a tab (see photo above)
that fits into this 'ridge'



Open up the points and check that they're not pitted.
Find the 'highest' points (both sides) of the cam-ring
and
check the points gap: should be 0.012" / 30mm
(check your manual for specifics and set accordingly)
There's a few variations of this set-up and adjusting method



For that you're gonna need either a special LUCAS tool
or you take a 1/4" and file it down so it's quite thin (there's VERY little room)

 

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Put mag in a vise.
Attach plugs to vise.
Make sure there's good contact mag-to-vise
and vise-to-plugs.



Put some duct-tape on mag.shaft to protect the thread and
attach an elec. drill to the shaft.

Run the machine ANTI-clockwise... repeat ANTI-clockwise
as seen from
the side where the drill-machine attaches/
the 'shaft'-side of the mag.

Here's a few second of video.
Unfortunately the sun was flooding in so it's hard to see the spark



What you want to see are FAT, HEALTHY, BLUE sparks !



Also; run it without the cover (as on video)
to see if there's any 'arcing' between the points.
(small spark jumping between points)

Now if you don't see that nice fat blue consistent sparking
or/and you see 'arcing' you're f*****.

Inconsistent sparks mean that there's
a break-down of insulation between the windings.

'Arching' between the points means a faulty capacitor/condenser
that you can not replace yourself.

Not much you can do but
send it off to repair.

You've now been officially taken prisoner
by to the Prince of Darkness!
 

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and just how were you able to find one of those bastards that still worked?!?!?! is it rebuilt?
 

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Great post! Always good to learn how to check lucas parts, one of the weaker parts of a triumph motor.....

----Andy
 

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Great write up, with video even! Just to reinforce a point here of something very well done that you did in the how-to: when you're testing a mag like this, ALWAYS have the plug wires hooked up with a gap (or plugs) to ground so that energy has somewhere to go. I can never stress this enough to people who try to test out their mags. To have the discharge go arc back into the coil itself or the mag housing causes some serious damage. Nice work.
 

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Discussion Starter · #12 · (Edited)
No this is the type of stuff I like logging in to see! Fantastic!
Thanks Scoot !

Just a little update as someone asked me
"..how to make the end that attach to my pick ups to get the best possible connection..."

Here's what you do;
..you need a couple of small washers,
preferably the brass type that are made specifically
for this purpose:



..pull the strands of wire through,
bend them out in all directions
and solder: (this one isn't too nicely done, but you get the point)



...and you're ready to plug it in:

 

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Thanks for bringing this thread back... I forgot about this. I'm working on a Lucas Mag right now for the first time and this is extremely helpful. Thanks again.
 

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So I'm having an issue that is frustrating me and my mag rebuilder. After a full rebuild my motor started right up, rode for 5 minutes, stopped, no spark. After a series of checks, I sent it back to the rebuilder. He got it and thought the ring the points rides in came out and just needed pushed in. Put 2 hours of flawless time on the bench. I got it back, spun it, sparked. Put it on bike, timed, no spark. There is no wire hooked up to the cap. What else could possibly be grounding this? Or what else could be causing this?
 

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So I'm having an issue that is frustrating me and my mag rebuilder. After a full rebuild my motor started right up, rode for 5 minutes, stopped, no spark. After a series of checks, I sent it back to the rebuilder. He got it and thought the ring the points rides in came out and just needed pushed in. Put 2 hours of flawless time on the bench. I got it back, spun it, sparked. Put it on bike, timed, no spark. There is no wire hooked up to the cap. What else could possibly be grounding this? Or what else could be causing this?
If you pull it back off, does it spark then?
 
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