NC1 Magneto

Hotspurr · Post by **Hotspurr** » Sat Sep 17, 2011 2:25 pm

Hi All,

I have a NC1 magneto on my 1957 AJS Model 18CS. How do I remember which condition is retarding it, slack cable or tight cable?

Thanks, Norm (Ann Arbor, MI)

Rob Harknett · Post by **Rob Harknett** » Sat Sep 17, 2011 2:53 pm

I believe that would be slack cable = retard. One sure way to tell is, start the bike. Advanced the engine will run faster, retard and it will slow down. Run the bike fully advanced when its warmed up, or it will be slow and heat up more.

Hotspurr · Post by **Hotspurr** » Sat Sep 17, 2011 3:03 pm

Thank you, Rob. That is my foggy recollection. I can't perform the test you suggested at the moment, since I have had the magneto off for repair and haven't had the bike running for a year. I need to know which way is retard/advance, however, to time the magneto. I'll give it a try the way you recommend and see what happens. When I get it running again I'll mark the lever as an aid to my memory.

aobp11 · Post by **aobp11** » Sat Sep 17, 2011 3:25 pm

Look at the points and their direction of rotation. Then look at direction of rotation of the cam plate or cam ring when you move the ignition lever. If it's in opposite direction then ignition will advance, if it's in the same direction then ignition will retard.
Hence, if the cable enters the magneto at the rear side (of the bike) then slackening the cable will retard the ignition. If it enters at the front side (of the bike) then same will advance ignition. This assumes that the points rotate clockwise when you look at the points (Lucas will say anti-clockwise when viewed from the driving side).
Albert

Hotspurr · Post by **Hotspurr** » Sat Sep 17, 2011 3:49 pm

Hi Albert,

The cable does enter the magneto at the front of the bike. When I tighten the cable it moves the cam ring in the same direction as the points rotate, i.e. clockwise when viewed looking at the points. So, from your first paragraph that means tightening the cable retards the ignition. That seems at odds with your second paragraph, or am I missing something?

Norm

rex.webb · Post by **rex.webb** » Sat Sep 17, 2011 5:10 pm

Moving the cam ring
"IN THE SAME ROTATION" as the MAGNETO goes .
"RETARDS THE IGNITION".
THATS IT !!
RIDE with CARE and LIVE LONG to ENJOY your BIKES or Scooter,s.
Insured with Peter James

Rob Harknett · Post by **Rob Harknett** » Sat Sep 17, 2011 5:49 pm

Starts to get confusing , A mag mounted at the front of the bike with with cable at the front. mag mounted behind the engine the cable is at the back. because the mags been turned round. Cant remember what mags on my old AJS's singles, but cable slack is retard, on my twin with mag at the back cable slack is advanced.

Don Madden · Post by **Don Madden** » Sat Sep 17, 2011 6:33 pm

N1, as used on singles up to mid-50s have the cable on the right as seen from the CB end & pull to advance. NC1, NR1, K2F, K2FC all have the cable on the left & pull to retard. Cheers, Don.

aobp11 · Post by **aobp11** » Sat Sep 17, 2011 7:41 pm

quote: That seems at odds with your second paragraph, or am I missing something?
Hi Norm, I wrote that with cable at front slackening the cable will advance the ignition, so tightening will retard, consistent with your first conclusion. (Perhaps the word "same", referring to slackening, is not correct English?).
Albert

aobp11 · Post by **aobp11** » Sat Sep 17, 2011 7:45 pm

Hi Don,
IIRC there was a position change starting 1952. [Was 1953]
I thought this topic has been discussed already but I couldn't find it via search.
Albert

According to Lucas catalog:
N1 42020A/D, plate 454600, cable at rear, -1952
N1 42272A/B, plate 464317, cable at front, 1953 (500) or 1953-1954 (350).
In Bacon's restoration book also both types can be seen in the pictures. Page 32, 1954 16MS, cable at front. Page 182, 1952 18S, cable at rear.
Edited by - aobp11 on 17 Sep 2011 7:26:39 PMEdited by - aobp11 on 17 Sep 2011 7:42:57 PM