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I have a 67 650 engine installed in a 69 royal star frame, engine ran great 40 years ago, Started it up again 4 weeks ago, with same points, same old points
plates adjustment, Idle was good
accerlataion was good,

I then disconnected the r/h coil to allow access to replace a scavenge oil line to the oil tank..

After doing this trying a restart It did not want to run at all over idle, Found a problem, I had some how reattached the positive leads to the negative on the R/H coi. l Not sure what damage this may have done to the points and coils/condensers

After I corrected this wiring I also replaced the the points plate with one which had better adjusters Concentrics

Timed adjusted for inital timing, with 015 thou dwell gap, but still not /unsure in my mind to where to time the point is open or when useing on the AAU timimg marks scribed with a well defined scribed line on the cam or is it the square notch also machined on the same aau cam. The Scribed marks to me indicate to me max point open/dwell, of .015, So at what point on the aau cam are the points suppose to open
I can probably figure it out but what is confuseing , is that i have a square 1/4 notch on my timing cam as well as a scribed line on mine

Last edited by andyame1974; 12/10/21 3:48 pm.
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what aau are you using ?
the stock 4ca aau is know to kill bsa twins ...
it screwed up production for all of 1967

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Its the 6ca with condenser pack under the seat. Ive read on here some people time the points to open on trailing edge of the square notch and some seem to say to adjust the points to just open at the scribe mark. I have it adjusted to the trailing edge of the square notch. It maybe ok at this but because i now have a miss going on now with the l/h cylinder and notice some bad sparking happening on that point while its running. Seeing as i have already replaced the condensers i,m going to now put in some new points and retime it all over again which may correct the miss. would like to see where others here are adjusting the point to open to be sure

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The AAU has to be locked in full advance and the points open at the timing mark on the generator rotor. Download a workshop manual from CBS.

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Yes i did all that, i have manuals coming out my ears, I would just like to know what mark on the aau cam is used to reference when points just open, the scribe mark to me is for with the cam locked at full advance which makes sense to me as the cam is then at its peak. The square notch i,m refferring to looks to me is the ramp up to the scribed line of the cam

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Ok i think i,ve over thought this, If the points are adjusted as you say with aau locked, gap adjusted to .015, the points will open at the correct time, I had been reading on here some others are refferenceing the point to open just at the trailing edge of the machined notch, kinda lead led me way off track, but still wonder what the notch is used for

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Originally Posted by quinten
what aau are you using ?
the stock 4ca aau is know to kill bsa twins ...
it screwed up production for all of 1967
Now after rereading this i am just assumeing the points plate is a 6ca, This one has the condensers in a pack under the seat, I thought the the point plate with the condensers mounted on them was called a 2ca, first time ive heard of a 4ca. My engine is a 67 with original AAU, How do i know what i have? Are there replacements available? Wish i went for the Pazon now, Its just because it ran so well before this i decided to keep with the old system and bought 2 new 12 volts coils

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Do a web search on 4ca Points plate. You will see they had the capacitors mounted on the plate.
The scribe mark on the cam is to show the high point. Align it with the heel of the points to check gap. I believe the notch is only there to rotate the cam when checking full advance. Easiest way is to put a washer under the bolt that fits over the pivot post and lock the cam at full advance then check the pointer on the generator rotor.

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OK thanks very much, I just googled the differences between the 4ca and 6ca before returning back to this site and seeing you reply Yes I somehow was mistaking the 4ca with condensors on plate as 2ca. Not sure which AAU i have, but did some more searching on here and read if you pull it off it should be labelled on the back as 12 degrees if i remember that correctly, If not will probably go with a EI system. That notch threw me way of track, Thanks for explanation on this, makes perfect sense now.

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Sorry for all last dramatics with last 2 threads and will try to explain, briefly as i can, After much time treating what i was sure was a ignition problem was in fact a carbureation problem, After trying all methods to determine ignition timing and still no joy , I did in fact find and substain very good idle. But if I tried to open the throttles just a bit the engine would die immediatley. This had to indicate fuel stavation, Checked the suplly from tank all good, float bowells full , Started looking at the carbs and noticed the l/h main metering rod was not moving with throttle slide, some how i reassembled this while fixing the float bowel leak, the rod came off the clip and fell through to only deliver a idle fuel flow and unable to react to any air demands, othere then bark want and die no matter the other side wanted when demand of open is being required.

Nothing is easy, I had this bike torn down, stripped repainted, engine built, and rideing in 6 months when i was 27, 40 years later this so much more detail, attention, attuned correct, Internet sites i see so much apllaude, Thanks for all Your inputs.

Last edited by andyame1974; 12/15/21 5:58 am.
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When I set points I set the gap at the scribe mark as previously described and then set the timing. You don't need to know at what point on the aau cam that the points open for the spark. You just set the engine in the correct and adjust the points plate until the points open. You can set the engine in the retarded position but it is better for the engine to be accurately timed for when blasting down the road fully advanced.

The point about 4CA destroying engine is to do with the aau rather than the points plate. Bikes ran perfectly well on 4CA until 66 or 67. I read a Triumph service sheet on this and it said the trouble only seemed to happen with a certain make of coils (not Lucas). When I bought my 67 triumph it had the full set of 4CA and seemed fine with whatever coils are fitted. To be on the safe side I changed the cam for the 6CA type but kept the 4CA points. They are a bit fiddly to adjust but work ok.

you can tell the 6CA aau easily because it is taller when viewed from the side. Also you need one that advances anti clockwise for a BSA, of course.

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The A65 cam does not have the AAU peg that the Triumph has so you have to get the timing close before moving the points or plate for timing.

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Quote
Sorry for all last dramatics with last 2 threads and will try to explain, briefly as i can, After much time treating what i was sure was a ignition problem was in fact a carbureation problem, After trying all methods to determine ignition timing and still no joy


Maybe I missed something but ,
Doesn't sound to me like you've properly timed to the engine ,
gapped the points or
ensured that the AAU is lubricated and not sticking .
... and more like you have found some random ignition timing ... where the bike starts .
( which is better than then not starting , but can be a long way from properly timed )

Have you strobe timed the beast ?
With strobe equipment where you can watch the advance spark move with rpms ?

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Yes was for sure having some mental blocks going on with the timing procedure, once i got it through my thoughts that the points gap needs be set first at the scribe line, like it says to do at the beginning of the chapter, then the rest of procedure is picked up again at the end of the chapter the light finally came on.

I had the AAU pulled out inspected and lubed, installed a used 6ac points plate just like what had previously but with way better eccentrics. Reinstalled it with the slots centered, found and centered the AAU, locked it down, Used a ohm meter to adjust the secondary plates one at a time to just open the points with the AAU rotated to full stop.

No i do not have a working strobe light, but it seems to running very well again now, and was hoping to ride it 60 miles depending how a test ride goes and save money on transport to the only good brit bike shop i know near me to fix the trany popping out of gear and replace the shifter shaft with worn splines.

Thanks all for your help

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I didn't read through all the replies, but it looks like you got way more than you asked for in your initial post. The simple answer to your initial question is that you set the gap with the heel of the points aligned with the scribe mark on the dwell cam. That's probably covered somewhere above, but now that you've changed breaker assemblies, timing procedure is required, which I'm sure is covered as well. To that I would just add:

- I think when you change from a 4CA to a 6CA breaker assembly, you're supposed to upgrade the AAU/dwell cam as well.

- Always re-check the points gaps after making a timing adjustment. In a perfect world, they would not change, but the timing setup on a BSA is anything but perfect.


Mark Z

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Originally Posted by Mark Z
- I think when you change from a 4CA to a 6CA breaker assembly, you're supposed to upgrade the AAU/dwell cam as well.

Your spot on, changing the points plate (wheher it be 6ca, 8ca 10ca etc) will allow you to get accurate adjustment across both cylinders which wasn't possible with the 4ca setup.

Changing the 11 degree AAU to the 12degree AAU has a different cam profile with a different dwell timing to prevent the points bounce which was causing the rouge spark and killing engines.

A strobe light is essential for anyone running a bike with more than 1 set of points, regardless of the vehicle.


Now let’s all have a beer beerchug

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

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In warmer drier countries like Spain motorcyclists , with old bikes which use points, build road side shrines where they can enjoy the roadside fixability of the original set up. I saw a lot of these shrines around the Sierra Nevadas, particularly Mulhacien. must be a lot of vintage enthusiasts there.At least that what my mate said they were for.

Last edited by gavin eisler; 12/17/21 4:27 pm.

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Originally Posted by gavin eisler
In warmer drier countries like Spain motorcyclists , with old bikes which use points, build road side shrines where they can enjoy the roadside fixability of the original set up. I saw a lot of these shrines around the Sierra Nevadas, particularly Mulhacien. must be a lot of vintage enthusiasts there.At least that what my mate said they were for.

What would these "shrines" provide - just shelter, or tools and equipment as well?


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Minimal shelter, usually some iconic religious figure because points need a lot of faith, a mirror for taking a long hard look, a packet of cigarette papers,for timing adjustment, a postcard for setting the points gap, a shot glass and some hard liquer. Sometimes a photo of a deceased relative to act as a medium for reaching out to Joseph Lucas.

Last edited by gavin eisler; 12/18/21 10:04 am.

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The only part of this I find hard to believe is that the shrines could remain stocked with liquor.


Mark Z

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Some also contain books on building totally original vintage and veteran motorcycles
and the joys of riding with wooden wheels, solid tyres etc. together with scrolls and
parchment documents on magneto rebuilding and how to earn/save enough money to do it.

Last edited by NickL; 12/19/21 10:40 pm.

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