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Nick H Offline OP
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Ok, the method Gavin told me about. Sheesh!


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Nick H Offline OP
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Well my cam timing looks good.

What I'm not confident about are my ignition timing marks on my rotor/stator.
If I set the timing advanced to 34 degrees BTDC, when I check it without advance it seems to spark right at TDC.
With an 11 degree AAU, shouldn't it be sparking at 12 degrees BTDC without advance?
This is what I mean about my questionable timing marks.
Recall that I don't have the luxury of a flywheel notch.

Why is it we go to the trouble to set timing advanced anyway?

By the way, I'm at least getting some pops now.

Thanks for the help thus far. I'm a bit dense sometimes.

Last edited by Nick H; 06/08/20 1:39 pm.

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Originally Posted by Nick H
Why is it we go to the trouble to set timing advanced anyway?

Timing at idle isn't as critical as fully advanced at high RPM. If your timing is off the mark at idle, you might have trouble getting the bike to start. If it's off the mark at full throttle, you might burn a hole in the piston. So it's best to assume setting full advanced timing will get the starting timing in line. If it doesn't, there are certain ways to increase the amount of advance offered by the AAU.

Do you care more about best performance at idle in the driveway, or passing trucks on the highway at 4000 RPM? wink

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With an 11 degree AAU, shouldn't it be sparking at 12 degrees BTDC without advance?


I think that's right, an 11 degree AAU will result in 22 degrees of advance, so that should be 12 degrees BTDC, but this is a rough approximation which is why timing is usually set at the fully advanced position.


Another inaccurate way to check is using a rod down the spark plug with a marking for where the fully advanced position is. I don't know what this measurement is on an A65 but you need to find TDC then turn the engine backwards so the piston falls past the marking and then forward until the mark is seen. As mentioned this is not very accurate and I don't know what the measurement is (maybe 0.31" ?) but it may give you a rough idea of whether your timing is in the ballpark or not.

Last edited by gunner; 06/08/20 3:31 pm.

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Why is it we go to the trouble to set timing advanced anyway

the full Advance timing is more critical to not putting a hole in the top of a piston
when the bike is running under load .

the idle advance position only needs to start the bike and provide smooth idle .
... with points set at full advance @ 34°
it's assumed that idle advance will be found mechanically when the AAU is unlocked .

you can try it the other way , set the aau timing "slack" at 12° ... this was one of the
old school methods ... before timing lights were common and home shops .

the Springs in your aau maybe to weak to hold 12° ... even at Kickstart RPM ?

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34 degrees is .304 inches BTDC......

or with the old school down hole method .
... 5/16" ... 7.7 mm

slack aau timing at 12° ... down hole is
0.0394 ... 3/64" .... 1mm

once the piston top is located or crankshaft degree is established
any factory mark from rotor to cover pointer should line up .
( if there is no rotor to cover pointer ... make your own )


maybe the aau springs are weak and the aau is advancing , even at kick over rpms ?
or
have you tried switching the plug wire leads ?

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Nick H Offline OP
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Well, that's two suggestions my AAU springs may be weak.
How would I check that? I have another to compare to.
Still curious why it seems to retard all the way to TDC when set advanced at 34. Or nearly - certainly not 12 degrees.
That gives me two different settings depending on whether I set advanced or slack.

Double checked the piston height. Dial bolted to exhaust.

Attached Images
tdc.jpg
Last edited by Nick H; 06/08/20 5:31 pm.

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I don't think there is an easy way to check AAU springs and it may be that the springs are from a different bike, hence the problem. I imagine that if you are finding its retarding all the way to TDC then either the springs or AAU/Points are knackered, worth swapping out for a different set but personally I would just fit an EI unit which would solve a lot of problems.


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I think you make a good "point".
I do have another set and actually I have a Boyer MKIV on the shelf. The later analog version that is supposed to be better for low battery.
Why am I messing around with these points then?!
Maybe because I fussed around with a Boyer MKIII for a long time on my Triumph before finally finding out it was defective or damaged.
Put points in that bike and started first kick.
I suppose I should give it another chance.

Last edited by Nick H; 06/08/20 6:23 pm.

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Still curious why it seems to retard all the way to TDC when set advanced at 34. Or nearly - certainly not 12 degrees
Nothing wrong with messing around with points ... if the AAU is taken apart and inspected and lubed .

piston travel isn't linear , it becomes less as it approaches top dead center .
@ 12° it's within 1mm.
@ 10° its 0. 69 mm
@ 8° its 0.44mm

as any aau is used , the Advance stop gets hammered ... and the stop at the end of slot opens .
an 11° aau eventually becomes 12° and gives 24° Of retard from 34 °
if set at full advance ... the idle advance will be less than with a stock new AAU .
( but this doesn't explain why your bike doesn't start )
... if the backing plate Advanced stop shows wear ... its worn .

Last edited by quinten; 06/08/20 9:12 pm.
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I maintain your setting the points at the wrong point.

If you’ve fitted the washer under the nut then the idea is that you use it to lock the AAU into the fully advanced position.

If your bike has the facility use the tool to lock your crank in the fully advanced position. If you can’t, then rotate the crank to the strobe timing mark. If you can have someone keep an eye on that mark, I’ve known it to rotate on its own weight and screw your timing up before now.

Screw the points plate so that the screws are centred within the slots. Have the AAU loose on its taper but screw still in place. Have the screw/bolt so that it is applying a bit of pressure or resistance to movement.

Remove the plugs, fit them back into the caps and rest securely on the head. Switch on ignition.

Use a flat blade screw driver and rotate the cam backwards (use the slot on the AAU and rotate it backward until the plugs spark.

Lock the bolt fully. Remove the crank locating tool.

If you haven’t already turn the engine until the high point on the cam (the scribed mark) lines up with the heel of the points. Set the points gap to 0.015”, then rotate the crank 360° and do the same for the other set of points.

Start the bike.

The timing will still be out by some extent. Do not at this point adjust the timing with the main points screws. Use the ones which are for isolated for each set of points.

Time both cylinders.

Set the points gap again. Check the strobe timing again and adjust with the larger screws holding the whole
Plate.

This is how I used to do mine and it was fine every time.


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Thanks Allan, I've basically done all those things except that I don't have facility to lock the crank fully advanced
nor do I have strobe timing marks except for those I made myself.

When I convince myself the current points setup is never going to work, I'll take this AAU out and compare to my other one
and maybe just install the Boyer at that "point".

Last edited by Nick H; 06/08/20 8:26 pm.

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One of the many mistakes I have made, when first timing my A65, assumed the points cam rotates the same way as the crank, it doesnt. Just a thought.


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Originally Posted by Nick H
Thanks Allan, I've basically done all those things except that I don't have facility to lock the crank fully advanced
nor do I have strobe timing marks except for those I made myself.

When I convince myself the current points setup is never going to work, I'll take this AAU out and compare to my other one
and maybe just install the Boyer at that "point".

I did remember part way through writing about your fly wheel being the wrong way around. One of my cranks was the same so I feel your pain. If you can make a piston stop tool this would help a lot.

As you don’t have any marks on your rotor apart from your own, have you tried turning the rotor around? There should be some marks on the other side of it.

If your timing the AAU at full advance it could be totally clapped out and still function, wobble with the cam on the shaft will cause erratic timing and weak springs will just cause it to advance early. The first you’ll feel when you have the unit in your hands, the second you’ll see when you rev it up on the strobe light. Eurotrash Jambalaya in the states sell really good springs (they sell good springs in general but obviously were on about advance springs) they go full advance at 3000, with a tweak I tightened mine up to 3500, the bike ran well like that.

Find the spark timing in the same method as I mentioned?...


Originally Posted by Allan G
Screw the points plate so that the screws are centred within the slots. Have the AAU loose on its taper but screw still in place. Have the screw/bolt so that it is applying a bit of pressure or resistance to movement.

Remove the plugs, fit them back into the caps and rest securely on the head. Switch on ignition.

Use a flat blade screw driver and rotate the cam backwards (use the slot on the AAU and rotate it backward until the plugs spark.

Lock the bolt fully. Remove the crank locating tool.


If you haven’t, give it a try, it’s imperative that you turn the cam so it’s opening up the bob weights, not the other way around I tried with the light bulb method as shown in the workshop manual, not only did I find it more of a faff but for some reason it didn’t want to work for me. This method works every time from Bantam to A65, it even works on bikes which use Hall effect sensors on the timing and the window on the rotor is quite large.


One other thing to check is that you have a BSA Type AAU and not a triumph type or unit single type. With the triumph/unit single AAU unit as soon as it starts to open up it will retard the ignition. The 11° AAU strikes me as puzzling, AFAIK A65’s (certainly all the later ones with 6CA cams) were 12° not 11°.


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Originally Posted by Nick H
Well, that's two suggestions my AAU springs may be weak.
How would I check that? I have another to compare to.
Still curious why it seems to retard all the way to TDC when set advanced at 34. Or nearly - certainly not 12 degrees.
That gives me two different settings depending on whether I set advanced or slack.

Double checked the piston height. Dial bolted to exhaust.


The 1/2 timing pinion rotates at 1/2 engine speed so 12 degs on the points cam = 24 degs at the crank.
Allowing for backlash in gears and wear in the mechanical assembly you may see a few degrees difference at
the crank/piston height.
Spend a couple of hundred bucks on an electronic ignition and life will be simpler.
My2c

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Originally Posted by NickL
[quote=Nick H]
Spend a couple of hundred bucks on an electronic ignition and life will be simpler.
Hmm, not necessarily. If the timing marks are non-existent then it's possible that nothing is lining up. Nothing will line up with EI either. Don't get me wrong, I'm a big proponent of EI but replacing points with EI shouldn't be "to make it work" but rather "to improve on the working process".

If replacing the points with EI helps in this case, then the original parts were wrong (either points or AAU) and a different set would have helped as well.

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Originally Posted by MarcB
Originally Posted by NickL
[quote=Nick H]
Spend a couple of hundred bucks on an electronic ignition and life will be simpler.
Hmm, not necessarily. If the timing marks are non-existent then it's possible that nothing is lining up. Nothing will line up with EI either. Don't get me wrong, I'm a big proponent of EI but replacing points with EI shouldn't be "to make it work" but rather "to improve on the working process".

If replacing the points with EI helps in this case, then the original parts were wrong (either points or AAU) and a different set would have helped as well.
Thank you. Exactly why I am reluctant to go to the effort to install the Boyer I have on the shelf here.
Also have some Lucas springs #54417992 which I think are supposed to be stronger springs
I feel points are somewhat easier to diagnose and troubleshoot.
If there is a problem with my timing marks, which I don't think so as I've checked them all different ways, then the EI won't work either.
Maybe it's a carb or other problem.

Alan: Here's my other BSA AAU, 11 degree. Maybe early 4CA part.
Curious. Doesn't have the hash mark to set points on the front.

.[Linked Image from i.imgur.com][Linked Image from i.imgur.com]

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Last edited by Nick H; 06/09/20 1:11 pm.

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From researching some old posts it does look like yours is a 4CA AAU. these are best turning into spinning tops for kids to play with, their cam design caused a lot of engines to go bang (the dwell is something like 170 degrees, the downside was this caused some points bounce and sparking to occur. The 6CA is something like 86°) for a few years until BSA realised the issue and come mid 67 created the -Y bikes which apart from the oil system upgrade also had the cam upgrade to 6CA. The points plate was also updated from the type which had the condensers mounted at the points, to a provision under the seat. This allowed the points to be adjusted/timed individually rather than setting it somewhere in the middle or adjusting the points gap on individual points in attempt to try and time the cylinders accurately.


Older Britbike post if you scroll down to RF Whatleys comments and have a read. RF is still a member of this board and very knowledgable on what rolled out of the doors of Lucas.


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Well that settles that! I'll be installing the Boyer. Hope it helps the starting too.
Thanks Allan for that esoteric bit of info! You may just have saved my engine.


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You are using NEW plugs, right?

The pod has nothing to do with this

Figure out how to run a jumper wire from battery to coil and eliminate all else

If you are using points as I think, are they CLEAN?

Any flim on the contact surface will screw things up.

Why are you messing with cam timing? Is this a new build or have you had the cam out?


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Originally Posted by Nick H
Well that settles that! I'll be installing the Boyer. Hope it helps the starting too.
Thanks Allan for that esoteric bit of info! You may just have saved my engine.

The Boyer is less faff to set up and fit and forget (I’m a Pazon advocate myself but each to their own)

I was hoping to find that I could find an image showing the cam looking like a triumph type but sadly in one way not so. So I stumbled across the old thread, it did teach me something also so that’s good news there, I thought they were ALL 12° but it seems not only the 6CA type.

Fingers crossed with the Boyer install. If this doesn’t work it might then push us all to look down a different avenue.

Another one to try if your sure you have it set right but it won’t go, open the throttle fully and crank it over like that, I usually do it with a flooded engine but a troublesome one it tends to work with too (providing everything else is correct)


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Originally Posted by MarcB
Originally Posted by NickL
[quote=Nick H]
Spend a couple of hundred bucks on an electronic ignition and life will be simpler.
Hmm, not necessarily. If the timing marks are non-existent then it's possible that nothing is lining up. Nothing will line up with EI either. Don't get me wrong, I'm a big proponent of EI but replacing points with EI shouldn't be "to make it work" but rather "to improve on the working process".

If replacing the points with EI helps in this case, then the original parts were wrong (either points or AAU) and a different set would have helped as well.


You can get it running with an EI by putting a screwdriver down the plug hole and marking it at somewhere around 8mm.
It's a bloody site easier than messing with the points cam, replacing springs, checking wear on advance assembly etc..
When i see a points plate/mech advance that isn't worn or clapped out on one of these old crates i'll advise to use it.

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Ooops, Wait! Looks like I had a 12 degree AAU in after all. Really must take notes in the future.
New plan is to put my strong springs on the AAU and give it another go. One strong spring, two?

Richrd: New points, new plugs. Yes, motor was apart.


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Always fit a matched pair of springs, so two.


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Do yourself a favour, once you get it started either go 6CA or electronic and dump the 4CA AAU.

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