The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: BSAlien on 27.10. 2017 20:59
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Dear all,
this is my first post in this forum.
As I have read a lot of things over all 4 years now and got really helpful informations,
I would like to give something back.
(Sorry for my English at all)
The camring of the K2F is locked by an excentric screw, which is not visible from the outside
and it is not listed in any documents of the K2F magnetos.
This invisible excentric screw again, is locked by a small rivet on the camring-housing.
If you drill this rivet (2,5 – 3,0mm drill) out, you can see a slotted screw.
This screw can be easily replaced by a longer one, which can be made of a stud bold (rockerbox cover of an A10)
So you can adjust the timing of the Magneto very, very easily without dismantling the timing-side-cover again.
Also during a test drive with just some little tools!!!
You can easily adjust the timing while you use a stroboscope lamp.
Hope the pictures can give you more informations, than I can right down here .
Cheers
Hubse
How can I post the pictures in here???
adm edit: If the picture question refers to pictures inside post \ text: until the new version of forum software is released (no date yet) pictures are added below the post. Just refer to them in the text (example: see pic1, see pic 2, or ref. attachment 1, ref attachment 2, or whatever that makes sense).
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Why did you drill the cap when it can be lifted out with knife blades?
Do not adjust ignition timing with that eccentric screw. It is for timing points opening to be correct in relation to magnetic flux. That is: the magneto’s internal timing. You are weakening the spark by wiggling it around to set your ignition timing.
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G'day BSAlien, *welcome*
Thanks for your insight to the timing of our K2F's but as TT said your mod will change the intensity of the spark. Now that you have "adjusted" it, it may be hard to get it back to maximum flux.
Beezermacc or Groily may be able to shed further light on the subject.
The best quick "fix" for timing I've seen is Orabanda's slotted magneto mounting holes.
Cheers
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Thanks for the invitation Musky!.......... mmmmm, interesting one! Strangely I'm in agreement with everything above, even though there are two sides to the debate. The eccentric screw is to make sure that the points open at the optimum moment relative to the magneto's internal flux. This occurs just after the cheeks of the armature pass the faces of the magnets in the body. If the points open too early you get no spark at all. The later the points open relative to 'peak flux' the weaker the spark gets, so the bike gets increasingly difficult to start. A good magneto will tolerate an inaccurately set cam ring as its surplus performance compensates for the weakening spark. However a poor magneto, i.e one with a weak spark already, will not tolerate late opening points as this makes the spark even weaker and the bike becomes impossible to start. I would guess that the eccentric screw is capable of moving the cam ring less than 10 degrees so, provided the magneto is good and the points don't open early, the magneto should perform OK. To test the effect of moving the eccentric screw you need to set the magneto up on a rig, run it at slow speed and turn the screw whilst adjusting the spark gap. A Vincent is a 50 degree V twin and uses a K2F, just like an A10, except that the cam ring is asymmetrical to ensure the points open at the right time for each cylinder. In fact the points open at 155 degree and 205 degree intervals. Remember that the points can't open early so the second cylinder is firing 25 degrees late, yet it still fires. Agreed, starting a Vincent takes a bit of practice but, with a good magneto, Vincent owners say they have no problems starting them. There is no way the eccentric screw on a K2F makes an adjustment anything like 25 degrees; and I'll bet the vast majority of magnetos on our A10's have not had the eccentric screw checked for flux strength. So, my conclusion is that you can adjust the timing with the eccentric screw but you might weaken the spark. If you weaken the spark sufficiently so that you notice the bike being more difficult to start (or any other dip in performance) you'll have to go back to the 'by the book' method. There are other reasons, fuel economy etc., why it is best to make sure the magneto is performing as effectively as possible so it is best to use the eccentric screw for peak flux adjustment rather then timing, but a 'slight nudge' one way or the other is not likely to make a lot of difference.
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As ever, all that B'macc says I agree with.
It's maybe worth just adding that with wear on the heel of the opening point and on the camring (or pushrod and camplate on a face-cam thing like a magdyno) you'll get some internal timing 'error' over time (compared to the maker's setting) so tweaking to get a fraction more internal advance isn't necessarily a bad thing sometimes.
Fitting new points or a new or different camring changes things again though. You can only really see the differences on a dynamic rig.
The difference in low speed spark performance between full advance and retard of the ecccentric can be more than you'd think although as B'macc says there aren't many degrees of movement here.
It is often possible, where a K2F won't spark the Lucas spec test gaps at the rpm specified by the makers, to gain significant improvement. Typically, there is an upside of maybe 30 or 40 rpm on the mag between 'late' and 'spot-on' on this screw, which makes a useful difference when trying to start, say, a Velocette with its low-geared kickstart, not to mention the problem with the late spark on the second cylinder of a V twin. That problem is compounded by the use of a manual camring on a V, where you can be asking the second spark to occur at 45° of retard compared to optimum (and it still works, albeit not below maybe 250+ rpm). Only the use of twin mags, or conversion to coil igniton with a distributor, will get round the unsuitability of using a device not designed to work asymmetrically.
The best I have ever seen a K2F do is 'all sparks across 3 point 5.5mm gaps' at 90rpm of the mag. Standard spec is almost all sparks at130rpm, excellent (to me anyway) is about 110rpm, a bit sad is 150rpm (double these numbers for engine speed). In all cases the beast will start, and the mag will make good sparks at the flick of a wrist. (When you think that some mags for commercial vehicles in the vintage period would produce their sparks at THIRTY rpm, it shows how effective these things can be at low speed!)
In the context of minor departures from performance specs, other things are just as likely to be relevant too, however. The magnetism, the state of the cb points, whether there is wiggle on the opening point's pivot, whether there is wear on the opening ramps of the camring (which denies the points a snappy opening) . . . and maybe above all the air gap between armature ad magnet on a several-times rebuilt instrument. All of which can have a worse effect than a minor maladjustment of the eccentric pin.
So yes, a modest tweak of the eccentric screw won't probably have much visible effect . . . but all the same, best to try to set it right and leave it there, I'd say.
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Dear all.
If somebody is using a manual controlled K2F magneto, you turn the camring to get the right ignition points
to start and drive on higher RPMs.
With the excentric screw it is possible to turn the camring over a range of about 5° at all.
Where is the difference in adjusting the timing between the "advance/retard control" and the excentric screw
by using an auto advance unit?
I can not see a difference in these mechanisms.
Cheers
Hubse
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You are right, in that retarding the spark with the hand trigger also weakens the spark.
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Well Hubse you certainly dropped a pebble in the pond with your very first post!
Welcome to the forum. *welcome*
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Lucas sought to improve the performance of the KVF magneto by fitting platinum points, rather than tungsten, as standard.
And BSA fitted platinum points to the 1961 Super Rocket, according tothis USA market service sheet, although I woild not order parts using those numbers which I think are for clockwise mags!
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Dear all.
If somebody is using a manual controlled K2F magneto, you turn the camring to get the right ignition points
to start and drive on higher RPMs.
With the excentric screw it is possible to turn the camring over a range of about 5° at all.
Where is the difference in adjusting the timing between the "advance/retard control" and the excentric screw
by using an auto advance unit?
I can not see a difference in these mechanisms.
Cheers
Hubse
You are quite right, there is no difference... they both cause weakening of the spark as they delay the moment when the points open relative to the position of the armature. If you set the A/R lever to full retard most bikes won't start at all because the spark intensity is almost completely lost (depends how far the lever can move, of course). The fact that the eccentric screw only moves about 5 degrees emphasises my point that it is possible to adjust the timing with the eccentric screw because the little difference it makes is likely to be unnoticeable to the rider. Even with manual advance you can set the eccentric screw to achieve points opening at peak flux. As groily said with reference to Vincents, they are 25 degrees late and even worse when you retard the ignition on the lever, but they still start (just about!). However, the best set of circumstances will give you the best spark at startup, and this is with the eccentric screw adjusted to peak flux and the timing set properly with the drive gear.
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Amen to that B'macc.
The only other thing I would say is that it is so worth checking the basic timing setting properly again after doing any playing.
Even a spoke down the plug 'ole 'n a bit of fag paper is good enough to show up small changes which, when doubled up at the crank, may amount to several degrees.
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Definitely. You always have to check the timing after you think you’ve set it!
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As some of the good family of the forum might recall, I advocate slotting the three mounting holes in the K2F body. If you are careful with a round file, it can be nearly as tidy a job as if it were done in a mill. You will end up with between 15 -18 degrees total movement, depending how close you take the end of the slots to the edge of the triangular mounting flange (ie how much "meat" you leave). So, if you end up with 16 degrees total arc, then set the timing (locking the magneto pinion on the shaft) when the magneto is in the middle of the slot. Therefore you will have 8 degrees of advance or retard available from that position).
Richard
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I quite readily did that as soon as I had the opportunity- works for me *smile*.....but If you are careful with a round file, it can be nearly as tidy a job ..........
oh yeah... *eek* *eek*
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Tsk Tsk Dutch, you didn't warm up properly; Three beers before the first hole would have steadied your hand.
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And by the third hole it would have been square!
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Dear all,
this is my first post in this forum.
As I have read a lot of things over all 4 years now and got really helpful informations,
I would like to give something back.
A few words \ pictures in the intro section ?
And interesting work on the magneto, nice to see experimentation skills.
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Puuuuh!!!
First of all,
I would like to say „Thank you!“ to everybody!
It is not so easy for me to read and understand everything at the first time.
Some of your postings, I had to read several times!
I will try to make a summery (please comment) for me and for all the others, who are interesting in this post.
Summery:
- You can adjust the timing with the eccentric screw, cause it is an easy way, if everything is mounted
- But, everything else should be fine and in good condition
- The eccentric screw is normally used, to set the optimum point of a bright spark / peak flux
(camring in position to the armature / point of opening contacts in relation to the most efficient voltage for the
spark plug).
- If you move the eccentric screw, you will change the intensity of the spark
- For adjusting the timing, this method is suboptimal!!!
Questions:
Is there anybody out there, who can tell us, how much the intensity will get lower, if the camring is moved out of its optimum position … may be for 2°?
Is it possible to find out the ideal position of the camring to the armature with home tools?
Cheers
Hubse
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As some of the good family of the forum might recall, I advocate slotting the three mounting holes in the K2F body.
You know what, I tried and failed to find that original post of yours Richard when thinking about Hubse's question.
Not only a great idea, but one I've done a few times too, as it makes life a fair bit easier on machines where you can get to all three mag fasteners without having to take the cover off and pull the gear or sprocket.
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hi guys, has anyone thought of using an auto advance system in conjunction with a manual magneto? if the manual cable was left off and replaced with a simple adjuster on the mag instead, timing could be altered that way, cheers
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Tsk Tsk Dutch, you didn't warm up properly; Three beers before the first hole would have steadied your hand.
Yea wanna bet I didn't- *smile* where d'yea think dutch courage comes from
And by the third hole it would have been square!
...ish... *eek*
I think I have photographic evidence somewhere... not sure if that's a good thing, but seems it worked out ok
*wink2*
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hi guys, has anyone thought of using an auto advance system in conjunction with a manual magneto? if the manual cable was left off and replaced with a simple adjuster on the mag instead, timing could be altered that way, cheers
This is something I regularly recommend to customers as you get 'the best of both worlds'. Set the ignition timing by wedging the weights open on the ATD and leave the cable slack. This means that you have the facility to retard the timing a little bit to prevent pinking when you're pulling up a hill. When starting the bike you don't use the lever to retard the timing as the ATD has already taken care of that. With regard to using an adjuster in the cable housing you are still moving the cam ring relative to the armature, so, weakening the spark; but provided you are only moving the cam ring very slightly there's no problem with this.
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hi Beezermacc, glad someone agrees i was waiting to get shot down. I intend to do this with my `Thorspark`set up as to get the adjustment if needed you have to loosen the rotor with magnets on and turn it a bit so i am going to replace my standard magneto with a manual one, has anyone else done that? seems a bit easier than slotting the mag holes, cheers
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Hello, Gents.
I've done the same as Kiwipom suggested on my A10. The reason being that there was a manual mag in the boxes of bits, and I did install the auto advance unit. I bored a small hole in the bottom of the 'mushroom' and fitted a spring, then with an adjusting screw and locknut, it's easy to get the timing spot on. The bike has always been a first or second kick starter.
Regards.
Tim.
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hi guys, great to hear that it works good raindodger, didn't quite understand the hole in mushroom bit could you explain in more detail with pic if possible, cheers
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hi guys, raindodger i have the original manual bits on the mag so i just need to fix a wire on to the plunger and attach it to a suitable adjuster, cheers
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Hello, Kiwipom.
Sorry, can't do pics, I'm a bit of a luddite when it comes to technology. However, I'll try to describe what i did. The part that I drilled is called the A/R plunger, there's a slot at one end for the cable and the 'mushroom' at the other which locates in a slot on the camring. I drilled a small hole in the 'mushroom' end and fitted a small compression spring which I stuck in with grease, and protruded about 1/4". The cable adjuster was removed and a long adjusting screw fitted in place with a lock nut. I found, initially, that the adjusting screw would catch in the plunger slot, but a small washer cured that. I set the camring to about half of it's travel and timed the engine in the usual way. Then the timing was checked and found to be 5 degrees late, 1 and a half turns on the screw brought the timing spot on. I'm a summer rider, I'm getting on a bit and don't like the cold, but in the 8 years since I rebuilt the old lady, she's been totally reliable and a joy to ride.
Best.
Tim.
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hi guys, has anyone thought of using an auto advance system in conjunction with a manual magneto? if the manual cable was left off and replaced with a simple adjuster on the mag instead, timing could be altered that way, cheers
Robbo's A10 was fitted up like that but was PIA, Musky should be familiar with that bike.
With the cost of manual end caps now days you could sell one and buy a new eletronic ignition and still have enough for a celebratory pint.
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The other issue with using a manual end housing is the wear usually found between cam ring and housing allowing some variation in points gap and timing.
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....... I set the camring to about half of it's travel ....
Hello Tim,
I think, you should set the camring next to the maximum advanced position for a maximum spark.
Can anybody confirm this?
Please have a look at the pic. It shows a camring in a normal housing with the eccenter screw in its middle position.
The end of the cam is just near to the top of the housing.
Hope everybody understand, what I mean.
Cheers
Hubse
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hi guys, Trevor when you say (manual end caps) what part are you referring to? if it is the ali end bit with the advance/retard on, that part needs the corresponding body as it is not the same as the auto advance body, DAMHIK, cheers
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Good question Hubse -
If you mean that you should find the best possible position of the camring at full advance, and then set the pin's position, then 'definitely yes'.
If you mean the pin should simply be set to let the camring go as far as it can go in the advanced direction, then the answer would be 'no'.
What you want is the points to open just after the point of maximum flux change, the 'flip' point, of the armature, in the fully advanced position. If you were to set the camring limit pin as far 'advanced' as it could be, then there is the risk of over-advancing and losing the sparks, especially at higher rpm. The magnetic lines of flux 'bend' with speed, so what seems fine at low speed becomes a problem at high speed.
There is also, sometimes, the need for a small compromise to make quite sure that the plunger that operates the camring can not disengage from its notch either at full advance or at full retard. Wear on the plunger, and sometimes on the notch in the camring, can cause this - and sometimes it can happen where a camring has been replaced and the notches cut just a tiny bit out of position.
It won't make a huge difference if the pin isn't in the absolutely perfect place, but the nearer the better!
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hi guys, Trevor when you say (manual end caps) what part are you referring to? if it is the ali end bit with the advance/retard on, that part needs the corresponding body as it is not the same as the auto advance body, DAMHIK, cheers
You sure on that.
I am fairly sure I put a manual advance on my original A10 and all that got changed was the end and from memory some shims
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Think the confusion arose if the end housing was square, using 1/4" screws, as opposed to rectangular with 2BA (or vice versa).
Housings from K2FC and K2F won't interchange, but like-for-like should be fine.
New housings aren't cheap, but there are some good CNC-machined ones out there, for the C versions anyway (not sure about the standard version).
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hi guys, Trevor just took some pics and as you can see they are different. I suppose you could make each fit the other if you were to drill/tap as required but these are the ones i have, also a couple that are not k2f, cheers
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Jools, these are the ones that I have do you have a corresponding mag body to take the same one as the manual one in the pic ,cheers
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Hi guys, a nice example of a manual ignition mag for getting fine timing adjustment, cheers
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Lovely job kiwipom.
'Chapeau!' as we say hereabouts.
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Lovely job kiwipom.
'Chapeau!' as we say hereabouts.
Not being a Fench speaker, (did metalwork and woodwork at our school; no foreign languages) I needed to look that word up.
Word forms: chapeau, plural chapeaux
masculine noun
1. (= couvre-chef) hat
un chapeau de paille a straw hat
tirer son chapeau à qn to take one’s hat off to sb
chapeau ! well done!
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hi guys, just to reiterate this is NOT something that i have done just saw it on another site but something that i will be hoping to achieve in the near future it is a nice job by someone else, cheers
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Lovely job kiwipom.
'Chapeau!' as we say hereabouts.
Not being a Fench speaker, (did metalwork and woodwork at our school; no foreign languages) I needed to look that word up.
Word forms: chapeau, plural chapeaux
masculine noun
1. (= couvre-chef) hat
un chapeau de paille a straw hat
tirer son chapeau à qn to take one’s hat off to sb
chapeau ! well done!
Chapeau melon = bowler hat. See why the bowler hat was never popular in France?
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G'day kp.
Is that an auto advance system with a manual "fine tuning" set up?
Cheers
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G'day kp.
Is that an auto advance system with a manual "fine tuning" set up?
Cheers
hi Musky yes I believe that is what it is,cheers
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Hello, KP
That's exactly the mod I did on my A10 mag, about 10 years ago. Goes well and never misses a beat.
Tim.
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hi guys, good to hear raindodger, the info that was attached to the pic indicated that the auto timing device was set at full advance then fine adjustment via the manual part, cheers