Britbike forum

Classic British SparesKlempf British PartsBaxter CycleThe Bonneville ShopLowbrow CustomsGirling Classic MotorcycleLucas Classic MotorcycleHepolite PistonsIndustrial tec supplyJob Cycle

Upgrade your membership to Premium Membership or Gold Membership or even Benefactor


New Sponsor post
10% Off Girling at The Bonneville Shop 2/3-2/9/23
by The Bonneville Shop - 02/03/23 6:14 pm
New FAQ post
News & Announcements
Premium members! 🌟
by Morgan aka admin - 02/04/23 2:40 pm
Buy BritBike staff a coffee ☕️ or pint 🍺
by Morgan aka admin - 01/15/23 9:29 am
Benefactor ✅
by Morgan aka admin - 01/08/23 8:38 pm
How to guides - Technical articles
ShoutChat
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Member Spotlight
Denis J
Denis J
Sacramento, CA
Posts: 485
Joined: November 2012
Top Posters(30 Days)
Lannis 84
DavidP 83
Top Likes Received (30 Days)
Kev. 34
DavidP 27
Newest Members
Uneasy Rider, Mally, Daveed, 70Triumph, Knight57Corv
12,392 Registered Users
Forum Statistics
Forums35
Topics76,551
Posts784,416
Members12,392
Most Online204
Jul 10th, 2022
Random Gallery photo
Photo posting tutorial

Previous Thread
Next Thread
Print Thread
Joined: Jul 2022
Posts: 47
Likes: 3
Britbike forum member
OP Offline
Britbike forum member
Joined: Jul 2022
Posts: 47
Likes: 3
I'm trying to educate myself on these BSA's until my eyes cross looking at the laptop. I picked up a fragment that 67 BSA's had the same issue with the 4ca points plate and the advance unit that Triumph had. Looking in my boxes of parts I see the advance is marked 11 degrees. I thought my 67 T120 was marked 12 degrees and found the 12 for the Triumph was OK. Is the BSA 11 degree the "OK " unit? Thanks, Gary


67 BSA A65L, 67T120R, 71 Hodaka 100B, 72 HD Aermacchi 350SS "cafe racer" 60 HD Duoglide, 77 HD FLH, 79 HD FXEF, 12 HD FLHTC
British motorcycles on eBay
Joined: Aug 2001
Posts: 6,111
Likes: 150
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2001
Posts: 6,111
Likes: 150
'67 BSAs still had the 4CA advance unit and breaker plate, so if yours is original that's what it has.

The 4CA breaker plate is easily identifiable; there are no "sub-plates" to adjust timing each set of points individually, and the condensers are mounted on the breaker plate. The advance unit is more difficult to identify, but the dwell cam profile changed, so it must be upgraded along with the breaker plate.

If you need to upgrade to the 6CA setup, you'll probably wind up spending more for the parts than it would cost to install an electronic ignition.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
2007 Triumph Bonneville Black
Joined: Oct 2003
Posts: 4,438
Likes: 30
Britbike forum member
Offline
Britbike forum member
Joined: Oct 2003
Posts: 4,438
Likes: 30
I kept the 4CA plate and used a later cam. The later cam is taller when viewed from the side so is easy to identify. A BSA one advances anti clockwise.

Dave

Joined: Aug 2001
Posts: 6,178
Likes: 302
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2001
Posts: 6,178
Likes: 302
If you like doing things twice then the 4CA plate comes with many advantages, not only is it fiddly to set up with accurate timing but it comes with the hidden bonus of poor cam design which creates rogue sparks, this greatly improves the chances of blowing up the engine allowing you to rebuild at your inconvenience at some point in the future. Another great feature for the tinkerer that comes with the 4CA are the internal condensers/ capacitors, these suffer from heat and fail quickly compared to externally mounted caps, and being part of the points plate construction they are hard to substitute with other caps .And lets not forget the points heel which rubs on the cam, subtle but so good for wear necessitating continuous monitoring of points gap closure and slowly drifting ignition timing great for roadside repairs, because unlike EI you can and will have to repair at the side of the road.
You can have even more fun tinkering with a badly sealed points chamber , oil ingress from the seal guarantees the need to clean and regap at regular intervals. Your fellow riders will truly appreciate an old school , hard core dedicated 4CA user , as they chat at the side of the road while the user performs its quaint repairs.

Last edited by gavin eisler; 10/09/22 11:44 am. Reason: caps. added sarcasm

71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
3 members like this: NickL, Shane in Oz, kevin
Joined: Aug 2001
Posts: 6,111
Likes: 150
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2001
Posts: 6,111
Likes: 150
Originally Posted by gavin eisler
You can have even more fun tinkering with a badly sealed points chamber , oil ingress from the seal guarantees the need to clean and regap at regular intervals.

Just to complement your statement gavin, note that the EI trigger mechanism cares not if there's a little oil present (which is commonly the case). And yes, this is another good reason to convert.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
2007 Triumph Bonneville Black
Joined: Feb 2019
Posts: 1,372
Likes: 489
Britbike forum member
Offline
Britbike forum member
Joined: Feb 2019
Posts: 1,372
Likes: 489
Originally Posted by gavin eisler
............You can have even more fun tinkering with a badly sealed points chamber , oil ingress from the seal .........
All Gavin's droll comments are absolutely spot on.

But, just to take this train of ideas for one more go round, the bushings on that hard working idler gear are known for wearing badly. On an old engine, this virtually guarantees oil leakage from the seal onto your points, AND, you get the additional aggravation of your ignition timing wandering as the load on that gear varies with rpm. I've seen it with my own eyes.

Originally Posted by Mark Z
.......Just to complement your statement gavin, note that the EI trigger mechanism cares not if there's a little oil present .......
Also true.

But, here's a little known EI failure mode that I'm not quite sure I believe, at least not yet.

On two recent desert rides, an EI trigger on a 750 Triumph quit sparking due to an alleged accumulation of magnetic dust on the working parts. Both times, hosing the points cavity out with gasoline or blowing it out with air got the thing running again. Anybody else have any thoughts on this? I mean, besides hollering BS.

1 member likes this: gavin eisler
Joined: Sep 2013
Posts: 4,023
Likes: 329
Britbike forum member
Offline
Britbike forum member
Joined: Sep 2013
Posts: 4,023
Likes: 329
Quote
alleged accumulation of magnetic dust

sometimes the rotor does not seat deeply enough in the taper

check the running clearance
between the rotor magnets and the
2 tangs that protrude from the bottom of the stator plate .

cant say off hand what the min running clearance should be ,
maybe 0.5mm ?
[Linked Image from feked.com]

Joined: Feb 2019
Posts: 1,372
Likes: 489
Britbike forum member
Offline
Britbike forum member
Joined: Feb 2019
Posts: 1,372
Likes: 489
Originally Posted by quinten
Quote
alleged accumulation of magnetic dust
..check the running clearance between the rotor magnets and the 2 tangs.......
That was my first thought too but when I asked, the guys had already looked and found no wear marks to indicate contact was happening.

Joined: Jul 2022
Posts: 47
Likes: 3
Britbike forum member
OP Offline
Britbike forum member
Joined: Jul 2022
Posts: 47
Likes: 3
Thanks for all the comments, even if they didn't answer the original question. I enjoy reading the fragments of information here from experienced BSA owners and always learn something from them. Sometimes I fail, learn from it, then hopefully succeed. Hence the "do it twice" name I gave myself.
I did find some info else ware on this site concerning the rogue spark problem with 67 A65L's advance units. Similar to the 67 Triumph issue that was solved by the factory after a given DU number. BSA did this and updated the advance unit if your motor serial # ends with a dash Y. If true, and since mine does and I can only assume its original, I'm probably OK unless there's a way to identify the advance unit. This might be true. Thanks, Gary


67 BSA A65L, 67T120R, 71 Hodaka 100B, 72 HD Aermacchi 350SS "cafe racer" 60 HD Duoglide, 77 HD FLH, 79 HD FXEF, 12 HD FLHTC
Joined: Aug 2001
Posts: 6,178
Likes: 302
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2001
Posts: 6,178
Likes: 302
the BSA is least worst.

Last edited by gavin eisler; 10/11/22 12:57 am.

71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Joined: Feb 2019
Posts: 1,372
Likes: 489
Britbike forum member
Offline
Britbike forum member
Joined: Feb 2019
Posts: 1,372
Likes: 489
Originally Posted by do it twice Gary
Thanks for all the comments, even if they didn't answer the original question. I enjoy reading the fragments of information......
You're quite welcome. It is all part of the Special High Intensity Training we get to go through so we can enjoy our British bikes. Sounds like you are beginning to get a handle on it.

On the auto advance unit, the early style lobe is recognizable basically as a circle with a flat spot that holds the points open for around 300 degrees, the later lobe is reduced to approximately 180 degrees that the points are held open. Someone hopefully has some photos to post.
The AA part number is 54419344 it is a 12 degree and advances counter clockwise. Nortons use this one too.
The points plate number is 54419097
You should be able to google those numbers and see what the parts look like.

1 member likes this: do it twice Gary
Joined: Aug 2001
Posts: 6,111
Likes: 150
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2001
Posts: 6,111
Likes: 150
Originally Posted by Stuart Kirk
Originally Posted by gavin eisler
............You can have even more fun tinkering with a badly sealed points chamber , oil ingress from the seal .........
All Gavin's droll comments are absolutely spot on.

But, just to take this train of ideas for one more go round, the bushings on that hard working idler gear are known for wearing badly. On an old engine, this virtually guarantees oil leakage from the seal onto your points, AND, you get the additional aggravation of your ignition timing wandering as the load on that gear varies with rpm. I've seen it with my own eyes..

Note here that the Triumph setup is not as bad as BSA, since on a Triumph the AAU runs off the exhaust camshaft, which is more stable than the BSA idler pinion. I say this because some Beezers may have had previous experience with Triumphs and may feel that the breaker point ignition is "not that bad".

Originally Posted by do it twice Gary
I'm probably OK unless there's a way to identify the advance unit. This might be true. Thanks, Gary
Correct me if I'm wrong Stuart, gavin, but I'm under the impression that the breaker assembly was changed at the same time as the AAU, to where there are sub-plates to allow for timing each set of points individually, and the condensers are moved from the breaker plate to under the seat.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
2007 Triumph Bonneville Black
Joined: Sep 2013
Posts: 4,023
Likes: 329
Britbike forum member
Offline
Britbike forum member
Joined: Sep 2013
Posts: 4,023
Likes: 329
Quote
I'm probably OK unless there's a way to identify the advance unit.

there are ways .

the 67 came as a complete 4CA Advance unit . ( condensers on the points plate and 86 deg points cam )
... but the 4CA points plate ( top ) is mixable with the later 6CA points cam .( bottom )

The 4CA Points cam ( bottom ) has 86° of dwell .
this cam is a round-ish shape .... with one flat of 86 degrees ( some people call it a D-shape )
... ( I don't know that this is always associated with 11° advance )
... so I would look at the cam-shape and not the Advance-stamp that the cam is attached to

thiis 86 deg. cam is what caused all the problems ... when run at 12 volts anyway ...for the first time in 1967
( the same cam was used for at least 3 years before , by BSA and Triumph and others ,
from 63 to 66 at 6 volts , without problems , )... I believe this same cam profile was also used in 18d2 distributors
( so used back as far as the mid 1950s )

At some time, mid-to-late in 67 , or maybe it was early 68 . bsa offered ... just the 6CA 160° points cam ( bottom half )
As a warranty fix for the problems with the 86° cam ... so for 67 ... it's fully possible that the Factory , a BSA dealer
or a home mechanic added the longer dwell 160° cam to the earlier points plate . (top )

160° of dwell makes the 6CA cam ... look more like an egg with 2 tips
( the closing ramp looks almost as sharp as the opening ramp )

by 1968 ... Lucas was making and selling the full 6CA top and bottom as a unit ... for new builds
... but you didn't get the 6ca top ( the points plate )
as part of a BSA warranty claim for bikes that we're already fitted with the 4CA unit ( 67 )
... you got only half of the improved part .... ( a kit with just the later cam and some kind of shim washer to better align the points arm )

None of this addresses the fiddliness of the 4CA points plate (top) ... which works if you know the process
And are willing to deal with it
But if you're just getting familiar with the 4CA points
... make sure you look at the bottom cam ... because it could be 4CA or 6 CA

1 member likes this: do it twice Gary
Joined: May 2013
Posts: 8,991
Likes: 305
Britbike forum member
Offline
Britbike forum member
Joined: May 2013
Posts: 8,991
Likes: 305
On BSA service sheets the 4ca cam was identified by having the 11 degree advance, and 6ca as having the 12 degree advance.


Life is stressful enough without getting upset over the little things...

Now lets all have a beer!

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (now rebuilt)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

1 member likes this: do it twice Gary
Joined: Jul 2022
Posts: 47
Likes: 3
Britbike forum member
OP Offline
Britbike forum member
Joined: Jul 2022
Posts: 47
Likes: 3
Thanks for the explanation. My 11-degree advance has the shorter duration profile so I believe I'm ok with it. gary


67 BSA A65L, 67T120R, 71 Hodaka 100B, 72 HD Aermacchi 350SS "cafe racer" 60 HD Duoglide, 77 HD FLH, 79 HD FXEF, 12 HD FLHTC
Joined: Aug 2001
Posts: 6,111
Likes: 150
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2001
Posts: 6,111
Likes: 150
Gary, unless I missed it, you still didn't say which breaker assembly you have.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
2007 Triumph Bonneville Black
Joined: Feb 2019
Posts: 1,372
Likes: 489
Britbike forum member
Offline
Britbike forum member
Joined: Feb 2019
Posts: 1,372
Likes: 489
I was digging through a junk box looking for something else and found these two, one old, one newer. The one on the left is the one that gives trouble, the other one is the improved one.

[Linked Image from i.postimg.cc]

Notice also that the early style is also shorter. Hope this helps.

[Linked Image from i.postimg.cc]

(They aren't both the same rotation btw but it doesn't matter for what we're doing.)


Moderated by  Jon W. Whitley 

Link Copied to Clipboard
British Cycle SupplyMorries PlaceKlempf British PartsBSA Unit SinglesPodtronicVintage MagazineBritBike SponsorBritish Tools & FastenersBritBike Sponsor






© 1996-2023 britbike.com
Powered by UBB.threads™ PHP Forum Software 7.7.5