ET: Engine (Twin) Seeking Ignition Suggestions For Twin - Can't Get The ATD Fitted

[ernie]

The ATD body carries the taper. It should be pressed onto the magneto taper, all the way back, before you tighten the bolt, though the bolt needs to be started on the thread so as not to be interfered by the ATD body. I usually tap the gear onto the taper with a large tube. Not a problem through the timing cover hole.

I don’t wedge the ears open any more. Using a degree disk I set 2 degs BTDC fully retarded. The magnets in the Magneto keep the heel of the CB on the cam.

 

[brian gains]

for repairs / servicing these guys got several thumbs up on another site I frequent. If they can't help maybe point you in the right direction.

Mainely Magnetos by Belanger's Auto Electric

don't know if still a going concern but at least your side of the pond, Maine ?

 

[CarlHungness]

The ATD body carries the taper. It should be pressed onto the magneto taper, all the way back, before you tighten the bolt, though the bolt needs to be started on the thread so as not to be interfered by the ATD body. I usually tap the gear onto the taper with a large tube. Not a problem through the timing cover hole.

I don’t wedge the ears open any more. Using a degree disk I set 2 degs BTDC fully retarded. The magnets in the Magneto keep the heel of the CB on the cam.

That suggestion (setting at 4 degrees, not two) has been made to me..and I'll go back and try it. But I re-checked my B-TH on the bench and it is sparking at low RPM, so installed it this morning and couldn't start it.

 

[CarlHungness]

Carl, here comes another idea: You got a BTH mag on the shelf with same taper shaft ? Get the ATD out and put it onto the BTH like you do on the bike: Tap it lightly onto the taper and then have the nut tightened while watching how much it pushes the ATD closer to the BTH case. Once a taper is seated it should never shift much more on a shaft by screwing the lot down. My thinking is, you got a crack in the ATD component with the taper so in consequence you can push it anywhere by force. And it will not keep the ATD at its timed position. At same time any flyweights may get stuck by deformation somewhere possibly - I don´t have a working Lucas ATD at home.
While waiting for your findings about this matter, have you come upon any defects around the carb troubles you seem to fight ? I am not current with present diagnosis on this.

Vic

I'm going to try to inst all the ATD ears closed and set the thing at 2-4 degrees BTDC. I just re-installed the B-TH
which is sparking on the bench, and got nothing. So I'll try the Lucas/ with ATD one more time and if I fail this time
I'm taking the engine out of the thing and taking it to Glen Bewley. I have 90 lbs compression as I've had for years,
even with new pistons head job a couple of years back..but Bill Jean screwed it up years ago and had my rear
valves hitting the pistons, he didn't check with plastilene...so I think it has plates under the barrells...it ought to have
better than 90, but as said..ran OK with 90. Will do another leak-down...but I'm so worn out I'm willing to go through
the drill of taking the engine out and starting fresh.

 

[CarlHungness]

for repairs / servicing these guys got several thumbs up on another site I frequent. If they can't help maybe point you in the right direction.

Mainely Magnetos by Belanger's Auto Electric

don't know if still a going concern but at least your side of the pond, Maine ?

Just talked to a great fella there and he says you have to have a spark of at least 3/8" to spark under compression. My B-TH sparks on the bench, but I'd guesstimate it's putting out a 3/16" spark at best. It's a tiny spark you can barely see. Thus maybe now I know why the B-TH won't fire it. Which leads me back to my newly rebuilt Lucas...I'll try to install it with the ears closed at 2-4 degrees BTDC and see if that works.

 

[oexing]

Carl, my posting was just about checking the taper part on the ATD if it has got a crack. I read your observations as if the taper can be pushed a lot more on the mag taper shaft after you have tapped it lightly on. That can only happen with a crack somewhere. And then the total ATD will not stay put and shift after starting. So for better seeing this I have meant to put the ATD on the BTH on the bench. In case you have lapped the taper a lot you may see a ridge on the shaft that prevents the ATD to sit snugly when cleaned from grinding paste. So then you´d have to remove that ridge by stone first before fitting the rest.

Vic

 

[CarlHungness]

Carl, my posting was just about checking the taper part on the ATD if it has got a crack. I read your observations as if the taper can be pushed a lot more on the mag taper shaft after you have tapped it lightly on. That can only happen with a crack somewhere. And then the total ATD will not stay put and shift after starting. So for better seeing this I have meant to put the ATD on the BTH on the bench. In case you have lapped the taper a lot you may see a ridge on the shaft that prevents the ATD to sit snugly when cleaned from grinding paste. So then you´d have to remove that ridge by stone first before fitting the rest.

Vic

I see no ridge. I have just re-installed the ATD on the shaft with the plot timed at 3 degrees BTDC...maybe it's 2 or four.
The MOMENT I 'set' the ATD on the shaft, the ears bind. No cracks on the bush on the ATD. I think the internals of the
ATD could be worn, thus the binding occurs the minute it goes on the shaft. I set it this time with the ATD ears closed, and of course they wouldn't open. I jiggled the ears, tapped, and got them to go free. Then when I finger tighten the
bolt, they stick again. Thus I fiddle some more, get the bolt very finger tight and they stay open. I put a socket on the
bolt and give it a 32nd turn and they stick...I can make them stick just by turning the bolt with my fingers. Thus in its
present state I am not capable of installing the ATD and tightening the bolt. So, I have the bolt in, as tight as I dare
and the ears are free to move open-closed.. I'll try to start the plot in the morning, and have a happy face while doing so.

 

[oexing]

Carl, seems you are one of many bikers struggling with the ATDs when mounting them on the mag. I cannot tell much about them, no working sample at home. But maybe you find that link below helpful, explaining a few matters you observed.

Vic
ATD tricks

 

[CarlHungness]

Carl, seems you are one of many bikers struggling with the ATDs when mounting them on the mag. I cannot tell much about them, no working sample at home. But maybe you find that link below helpful, explaining a few matters you observed.

Vic
ATD tricks

This guy certainly seems to speak fluent ATD and my problem sure seems to be the norm, and imagine he
can straighten it out. Bad news is he doesn't do any work June July August. I'm thinking about the Sussex conversion:

V-twin Electronic Ignition Kit 12 volt, Lucas KVF, for V angles 22 to 80 degrees Vincent, JAP, BSA etc

V-twin electronic ignition kit for the Lucas KVF magneto as fitted to Vincent, JAP, BSA, Morgan and others. It is suitable for engines with a V angle of 22 to 80 degrees. We can adapt this kit to fit other model V-twin magnetos as well, and also to fit in one of your magnetos if you have two...

www.sussexmotorcycles.com

 

[Simon Dinsdale]

This guy certainly seems to speak fluent ATD and my problem sure seems to be the norm, and imagine he
can straighten it out. Bad news is he doesn't do any work June July August. I'm thinking about the Sussex conversion:

V-twin Electronic Ignition Kit 12 volt, Lucas KVF, for V angles 22 to 80 degrees Vincent, JAP, BSA etc

V-twin electronic ignition kit for the Lucas KVF magneto as fitted to Vincent, JAP, BSA, Morgan and others. It is suitable for engines with a V angle of 22 to 80 degrees. We can adapt this kit to fit other model V-twin magnetos as well, and also to fit in one of your magnetos if you have two...

www.sussexmotorcycles.com

Carl
That Sussex conversion is the Thorspark which you have asked about before. It’s a simple module that replaces the magneto points with a pickup to fire an external ignition coil. It still uses the magneto armature as a rotating shaft but the armature no longer creates the spark. also it still uses the ATD to advance the ignition timing as there is no electronic advance. So you will still have the problem of your ATD slipping and not fitting properly and so the Thorspark / Sussex system will not solve your problem.

You have proven the fitting of the ATD is your problem, so the solution is fix / replace the ATD. Unfortunately they are not a simple fix when the taper in the ATD where it mounts on the mag shaft is worn. I fitted a new ATD to my Rapide 10 years ago due to a similar problem and since then I have not needed to alter the ignition timing as it has never moved.