The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: Clive54bsa on 24.07. 2018 03:50
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Hi Everyone, it's been a while since I posted on this site.
A friend of mine is restoring a '61 Super Rocket, and having only restored bikes with points and coil ignition, he asked me, as I have 2 A10s, if I'd help him time the magneto while his engine was on the bench with the head off. So "easy" I thought, but when I got there he had the steel points backing plate, and I was only familiar with the brass ones. Are the steel ones interchangeable withe the brass ones? The steel ones have a different center bolt, without the tapered shoulder. I was unable to remove the points plate by removing the center bolt as I do with the brass ones. so it made me wonder if they are interchangeable. Also if anyone has a blow-up picture of the steel type showing the placement of insulating washers etc, that would also help greatly.
Thanks all
Clive
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I've certainly had both steel and brass on my 1961 A10 SR over the years, just need to check rotation direction.
I've the brass ones on mine which I prefer as the spring was on the live side of the contact breaker on the steel ones SRM fitted and the slightest distortion saw it earthing to the case and stopping the spark.
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They interchange. The centre bolts are different (taper on ones for brass, under head of screw) as mentioned - and the steel ones are often harder to wiggle off than the brass ones. The 'live point' thing is well worth noting - spring kissing camring = spark free zone. Slots in spring should be long enough to allow correct clearances all round . . .
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I'm a little confused. When I time the ignition I loosen the ATD unit, not the points. Maybe you are wanting to change the points?
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The brass points are more robust than the steel ones with their rivetted construction. Steel were called low inertia.
Original Lucas steel points came with the necessary fibre washers and push ring, which dont come with pattern points as the makers have decided that we do not need!
The fibre washers beneath the moving point are to align the contacts and are hard fibre not soft.
Diagram of assembly and photo showing what Lucas used to supply below.
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Thanks for the info everyone, Greybeard, I wasn't trying to remove the points to time it, I noticed, as Groily pointed out, that the spring was very close to the cam ring and wanted to adjust it, but by removing the center bolt and points adjuster screw I was able to swing it out far enough to adjust the spring to give enough clearance. The points plate was stuck tight, so I didn't want to risk damage (not my bike). So after everything looked good, I timed it the usual way using a DTI on the piston crown.
Thank you Julian, that diagram and the Lucas box was just what I wanted.
Clive