1966 G12 Lucas 4CA Points and Timing

[nomisimon]

Hello, my G12 is fitted with the Lucas 4CA points system and dual coil ignition. I'm working my way through the bike and I'd like to check the auto-advance unit behind the points plate. I'd like to lubricate said unit and the pivot posts etc. I doubt they've been touched in many years.

I can't find anything specific to this points setup in the manuals in the Jampot Archives, apart from a similar setup on similar Norton twins. Does anyone have a copy of, or can point me in the direction of, an article of some sort on this setup?

I can see the points and check the gap, but would like to remove the points plate to check the auto-advance, without affecting the ignition timing. Is that possible?

I'd appreciate any help on this...thanks.

Simon Robinson

[Groily]

The 4CA with single or twin points went on a load of 60s machines from Tiger Cubs through unit Beesa twins and singles to the post-magneto Norton Atlas.
From 1964 (I think) the now-12v non-CSR models used the twin points in a housing that sat where the magneto would have been. Prior to that I think they had a typical single points distributor with a two lobe cam.

Haven't seen one like yours personally but the plate with the points mounted on should be removable by undoing a couple of screws and unhooking the advance and retard springs to reveal the weights etc behind, and you won't need to reset the timing from scratch after removal if you put it back as it is after ministrations - and haven't removed the drive gear.

New points assemblies (not the AR bits though as far as I can see) may be available but some suppliers currently list them as out of stock.

[nomisimon]

Hi Groily, thanks for the info. Yes, I remember they were fitted to many different bikes, but maybe not as hard to get at as on the G12. Like the 18D2 distributor which preceded them, the points are fitted where the magneto used to go. I'm hoping that somewhere, there's a copy of the official Matchless or AJS paperwork for the installation, as part of the 1966 owners manual possibly. For now, I'll carefully and minimally lubricate the points pivot and check the points themselves are clean, not pitted and properly gapped. Right now I need to resolve the 'difficulty engaging first gear' issue that seems common on AMC boxes.

[SPRIDDLER]

I'm hoping that somewhere, there's a copy of the official Matchless or AJS paperwork for the installation, as part of the 1966 owners manual possibly.

Is this any help?
Pages 76 and 77 in the manual here:
http://archives.jampot.dk/book/Owners_m ... Manual.pdf

Distrib 18D2.JPG

Right now I need to resolve the 'difficulty engaging first gear' issue that seems common on AMC boxes.

You probably know this but as an aside, gear selection difficulty is often due to a dragging/badly adjusted clutch.

[nomisimon]

Thanks Spriddler, but my 1966 G12 is fitted with the Lucas 4CA points system and dual coil ignition. There is no 18D2 distributor. I'm using some Norton info right now, but feel sure that AMC will have produced something, back in the day. Like you, I thought the gear selection issue was the clutch...and believe me there were problems with it; centre nut loose, shock absorber screws loose, shock absorbers melted and clutch soaked in oil. The whole clutch was flopping around on the shaft. I dismantled the whole thing, cleaned and dried the clutch parts, replaced the shock absorbers, reassembled it all correctly and the problem still exists. Other forums suggest loads of potential causes but worn layshaft bushes is top of the list, according to Mick Hemmings.

[SPRIDDLER]

Thanks Spriddler, but my 1966 G12 is fitted with the Lucas 4CA points system and dual coil ignition. There is no 18D2 distributor.

Ah yes. I misread your mention of the 18D2.

Like you, I thought the gear selection issue was the clutch...Other forums suggest loads of potential causes but worn layshaft bushes is top of the list, according to Mick Hemmings.

Hmm, I've not had an AMC 'box but with the B52 'box one occasionally has to ease the bike back a bit to get 1st to engage.

[clive]

.......I'm using some Norton info right now, but feel sure that AMC will have produced something, back in the day. .......

Manganese Bronze had taken over in 1966 and the company was now Norton Villiers so perhaps not. Norton stuff likely to be correct I would have thought as they had been owned for a while by AMC before the collapse.

[nomisimon]

Spriddler - yes, I did try that to no avail. Goes into second no bother, then back into first when moving. I'll start another topic on it.

Cilve - you may be right as I've never come across anything.

If anyone has a bike with the twin 4CA points and twin coils, I'd appreciate a chat.

[mdt-son]

If you are truly looking for information, I can recommend Lucas Service Information SB519 (issued around 1972). There is a brief paragraph on the 4CA/6CA contact breakers in the P11 maintenance manual. Consider swapping your 4CA points plate for the 6CA version, as it allows precise timing of each cylinder. I am using model 10CA on my bike (external condensers). Beware that the AAU may need an overhaul. These units do wear. Obtaining the correct replacement is almost impossible (AMC made few standard twins between 1964-66) and I had to resort to using AAUs for Triumph.

The contact breaker housing was an AMC development which was improved for the P11. Housings of the improved type are available from Andover Norton.

- Knut