hope not to kick against any sore shins, try the ignition form another approach (perhaps even simpler?):
- set the nr 1 cylinder at TDC as per usual
- retard the crank only 8 degrees (ccw).
- set the mag with the points at the correct lobe, just at the cracking point (light on/off).
- mount the ATD on the mag without disturbing the mag. DO NOT advance the ATD fully, leave it at rest or fully home in the most retarded position.
at least now you know that the static ignition is at 8 degrees BTDC, and not even retarded few degrees ATDC.
I did this to my rapide after fidgeting at 38degrees BTDC and ATD full advance etc., and it works pretty well! the old ATD will have indents to where the advancing arms hammer into the other arms. this affects both variable timing range and starting point.
why: the Enfield has identical bore and stroke and even similar compression ratio and valve sizes, so a very good comparison. there it is set at 8 degrees BTDC, works a treat.
going into detail (its pretty much geometry):
measure the diameter across the ATD where the advancer has indented its max stops. divide by 2 to get a radius figure.
then measure the gap between the advancer and the stops (this is the range in which the ATD can vary its timing).
you have 2 radii and a gap, and the triangle it forms has a small included angle. calculate that angle (here comes the geometry into play) (will be in the range of 10-15 degrees).
multiply that angle by 2 will give you the timing range of that ATD. let call that angle beta.
therefore: setting max advance at 35degrees BTDC will give you a (35 - beta)degrees static at low idle. for example, beta = 26degrees. the static will be 35-26 = 9degrees (the larger the static advance the higher the chance of getting kick-back).
setting the ignition form static approach: 8 degrees BTDC + beta = 8 + 26 = 34 degrees.
should you have a new ATD without indented arms the range is less than a worn example. therefore, if timing set at max advance, the static can be more and give you a potential kick-back.
anyway, just an idea.
my ATD is worn a bit and set at 8degrees BTDC static, giving a max advance of 38degrees.
what I do do is tie a thread from the ATD to a heavier object so all the slack in the drivetrain is removed when setting the timing.
note: picture inserted is showing my ATD at max advance and slack out of the drivetrain, when setting at 38degrees BTDC.
I think what you are saying is not to use my spark plug stop that sets the plot at 35 degrees, rather go
through my drill of TDC, then back it up only 8 degrees with ATD closed. Your photo shows the ATD fully
open, (ears held by a Ty-Wrap and weight on the ATD to take out the slack, correct?) It had been suggested
I follow what you've said, only to use 4 degrees BTDC, not 8. The writer noted I may get some pinking out
of the engine with such a setting. Then too I understand it is not unheard of for the cam pinion to slip on the
cam proper and at the moment I don't have the knowledge to check if that's what happened. We know for
fact the new ATD has 1/4" separation between the ears, and the original was 5/16". I have never re-checked
timing in past years when I installed the ATD (or the B-TH). I have always put the ATD on, ears blocked open
set at 39 degrees, light flickering, never used a bolt in the earth brush hole previously to hold the armature, now
I do and it's bitch to finger tighten it and keep the light OFF..light wants to go ON every time I finger tighten.
This time after setting the new ATD and no result, I re-installed the piston stop after getting to TDC, backed
it up to allow room for the stop, put it in, put piston against it, looked at the magneto and the SHOE sure
seemed to be in the original place I set it for my now 35 degree mark. The 'mark' is just damn close to the
old 39 degree mark, my old pencil mark still there. Thus it seems as though the shoe is at the 35 degree mark
where I set it originally with the ATD ears blocked open. Shouldn't the shoe be many degrees away from that mark
(in a clockwise direction) if in fact the ATD advances the mag?
I checked the timing to see: Did the ATD slip on the mag shaft, am I certain I set it at 35 degrees. The ATD
did not slip far as I can tell, it went on perfectly, using ONLY the bolt, NO socket to set it as I had done in
past years. So I'm asking just why in the Hell the bike started last week, ran great for 60 seconds and quit.
I got an ultrasonic cleaner today, took off carbs, cleaned them, and once again, no result. No pop, no kick back.
I'm getting spark, took out rear plug, held it on the Britax bar, kicked it and can see spark.
Have had the pipes off 7-8 times, drain oil, take off timing chest, and on and on...will do it all again, but have to
get some knowledge on how to actually check the cam timing to see if something has slipped on a shaft.
Really appreciate the suggestions. I am supposed to be practicing my oxy welding aluminum and haven't
fired the torch in a couple of weeks.