The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: RichardL on 06.07. 2014 21:45

Title: Magneto bad all of a sudden, and then, only sometimes?
Post by: RichardL on 06.07. 2014 21:45
Gents,

Due to my inability to achieve a reliably starting engine, I've been embarrassed to raise head up since completing my engine rebuild a couple of months ago. Also, other life events have prevented having time and good concentration to focus on the problem. I am going to try to tell this story as foreshortened as possible, while seeking some thoughts from the group.

On first timing, no firing and spark was rare or erratic. 

Replaced wires, caps and plugs.

Retimed and kicked it over with the ATD wood peg accidentally in place (causing full advance) and she started.

Retimed and reset points gap and she started up first kick, but I noticed that the large washer (behind the horseshoe washer) was not seated properly over the two pegs. Loosened ATD bolt and set the washer. Kicked it over again to be sure this had not changed the timing. Started first kick. Now, with confidence that I was finally there, mounted the outer timing cover (using sealer and my last gasket).

Moved the bike to position in  the garage where I could run her longer while exhaust left the garage. Started first kick. Stopped the engine for some reason I cannot recall. Since then, not a single pop of ignition.  Pulled the plugs and, at first, no visible spark. Slid some paper between the points to clean them. After that I could get some visible erratic spark, but can not be sure the cleaning was the reason. Plugs back in, but no firing.

This is a very partial description of the sequence of events, but I have tried to pick details that might lead to ideas.

The thing that makes me craziest is that, when I disassembled the bike for the rebuild last year, the magneto (with its Brightspark EasyCap) seemed to be working perfectly. The bike started easily, hot or cold.  Nevertheless, this new problem seems somehow magneto related, but I cannot understand the three most recent easy starts if the magneto is shot.

Wow! I hope someone has a super-obvious answer that embarrasses the hell out of me for not catching it but, at the same time, leads to bugs in my teeth before they go dormant for the winter.

Richard L.
 
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: wilko on 07.07. 2014 00:30
 Try another set of plugs.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: bsa-bill on 07.07. 2014 08:46
Quote
Try another set of plugs.

Yep - I'd would suggest also the most common cause these days.

Brought my Flash which was  in the bottom shed into the garage a distance of 30 yards for a repaint, we now need the garage for storage so had to take it back (still not painted), the normal first/second kick Flash refused to even hic - plugs - looked like a sweeps armpit, short run - sooted up and no distance to get up to heat I suppose, also maybe to rich on tickover?.
Anyway 2 new Bosch plugs - Baroom - I'm becoming a fan of these Bosch plugs, maybe Bosch haven't got around to out sourcing them too some third world nation as yet
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: duTch on 07.07. 2014 13:51

 Heya Richard- was wondering if I'd just slipped under a rock or something- been a few times when I could've used that green 'Cone of Silence' of yours.... *smile*
 Can I suggest maybe a intermittent earth 'lackage'....earth brush??

 Bill,
Quote
maybe Bosch haven't got around to out sourcing them too some third world nation as yet
you've been under my rock- I whacked in some Bosch plugs, but had to buy from two different places.
 Realised after a year that one is 'Made in Germany', the other is 'Made in India'.
Funny thing is- guess which one didn't sound right....?
  Not sure if any things wrong with it but swapped out for matching B7ES, much better, but enough of that here.
 
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: RichardL on 07.07. 2014 16:34
During the rebuild, I replaced NGK B7ES, with 3500 miles on them, with a new pair of the same. I'll try to pick up some Bosch plugs, but my gut tells me it goes deeper (or even stupiderer *pull hair out*). Really, I hope it doesn't, go deeper, that is.

I am now wondering (among other things) if the springs behind my slip-ring pickup brushes are properly seated. Any thoughts on the right way to get the big ends into the holders? I just kept pushing with a thin screwdriver.

In case there are any questions about my new caps and plug wire: caps are Rajah-type with a screw compressing the wire directly to the plug clip; wire is Packard 440.

Richard L.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: bsa-bill on 07.07. 2014 19:18
Richard I don't think Bosch are so good that they will never soot up under any circumstance , just I've run with them for a year or two without problem in my other Rocket morphed Flash and it had a history of killing plugs and disappearing spark.
In the case of my ever reliable Flash sooting up and not starting any clean plug would have solved the problem
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: beezermacc on 07.07. 2014 19:46
When fitting the Easycap it is necessary to cut wires and solder etc. My guess is something has gone wrong in the Easycap fitting process, maybe a poor solder joint or something in the low tension side tripping to earth, or something dodgy with your points. It doesn't sound like plugs. A good mag should fire through most half-decent plugs.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: RichardL on 15.07. 2014 00:48
Guys,

It sounds stupid, but I've been really thankful for a lot of bad riding weather here in Illinois. Makes me less aggravated that I haven't had enough time to get my bike on the road.

I just stoled some garage time to try to look at my problem with fresh eyes. I pulled the points out and everything looked OK there. I checked the cam to see if it was loose and, sure enough, it was. This was the first time I've had the cam out of the mag. In 3700 previous miles, two engine rebuilds and two magneto rebuilds (well, sort'a, rebuilds) it wasn't an issue.

I found this post from none other than Groily. http://www.a7a10.net/forum/index.php?topic=8393.msg59476#msg59476. Touches on my questions quite specifically about how the cam ring is held in position and held in. I looked at my bakelite cover and damned if the o-ring wasn't missing. In any case, I had started up at least once with the cover off, probably sending the cam off the pin anyway. I haven't taken care of it yet or retimed, but I still have a question: With the cam all the way in and the notch aligned with the pin, there still seems to be play in the cam between notch and pin, maybe two or three degrees. Is there a good way to snug this up?

Thanks, in advance, for your thoughts.


Richard L.


Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: duTch on 15.07. 2014 04:07

 I'd only be guessing if I say cable adjustment....? That is if it's manual Adv........?
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: RichardL on 15.07. 2014 04:14
Dutch,

You have accurately pointed out that I forgot to remind the team that she has an ATD. So, no cable. Nevertheless, thanks. Any other ideas? I just don't see as how it makes sense to have the stability of timing dependent on the notch in the cam straddling less than half the diameter of the pin for holding its location. Have I described this correctly? If not, maybe there is something else going on here.

Richard L.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: duTch on 15.07. 2014 07:49

 Hmmmmm- I think mine has two pins about maybe ~1/4" apart.....maybe a small blob of silicone? At least till you come up with something better.?
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: groily on 15.07. 2014 08:05
Hi Richard,
You don't want several degrees of float on the camring, for sure. It might be possible to eradicate it by shifting the pin's position a bit  . .  . to do that, prise the little cap off the top of the pin (it'll come without damage, v fine chisel or screwdriver), to expose the slotted head of a threaded item with an eccentric on the inner end. The eccentric is there to give fine tuning of the camring position, and will have been set to the best position for best sparks at the factory. However, chatter over the years might have worn it a bit. Because it's eccentric, you should be able to turn it a little to get the eccentric bit to fill the notch a bit better without moving the camring more than a gnat's whisker (which will be OK).
Quite often, I've made new eccentric-ended screws to eliminate this hassle.
The pin in the outer end acts as a locking device, as you'll see, by expanding the slotted outer end of the thing so it doesn't move. However, a short bit of threaded with a little locknut works just as well, and in fact you could make a bit with a file to engage exactly with the notch in the camring. Then screw it in and refit the camring. Thread is BSF, 5/16 from memory.
Also, would suggest you make up a gasket or seal thick enough for the end cover of the cb housing to pinch against the camring, to stop it fretting if it's so inclined. Often, the seals supplied or fitted don't actually engage the camring at all.

If the camring is a very loose fit in the end housing, then it might be worth using a dab of loctite on a fixed mag. The risk with loose-fitting camrings is that the firing interval between cylinders can be upset by several degrees if the ring is off centre (quite apart from there being a noticeable difference between the points gaps on the lower and upper lobe of the cam). Perfectly equal gaps are less important than 180:180 firing interval (as long as the smaller one is c. 12 thou) - but the firing interval is hard to measure. A static test can be done with a rotary table and a buzzer of the Brewington sort, but proper dynamic testing requires more serious kit with rotary spark gaps and a protractor to see what happens up the rev range, when things can look rather different from at rest
In this regard, it is also worth looking closely at the pivot for your moving cb point. Wobble on there has some of the same effects. If very worn, the pivot post can be replaced (fiddly); if not too bad, a new set of points might help.
Hope that helps a bit. Not sure that any of this will bring the sparks back however, unless there is a short on the LT side for one or other reason.  My mate KenF might chip in if I've missed anything  . . . Cheers, Bill

Just seen Dutch's  . . . only early mags have the axial screws for limit stop operation - they don't have the eccentric bit. Suspect you have the later sort Richard?
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: RichardL on 15.07. 2014 12:35
Bill,

That's a fantastic lot of knowledge and , I think, just what I needed to know. I'll know better after I implement the advice. Thanks, greatly, for taking the time to write it. By the way, The symptom in my last go-round was that, after timing, it started on the first kick three times in a row, then, wouldn't even cough. This seems to fit the moving cam-ring diagnosis.
 
Richard L.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: beezermacc on 16.07. 2014 20:22
In my opinion the slack cam ring isn't going to stop the mag sparking unless it has floated off the peg completely. Don't forget that a manual mag provides for about 10 degrees retard by rotating the cam ring to aid starting, so the little bit of unwanted rotation on your cam ring isn't going to make a lot of difference. The problem still sounds like an intermittent short or open circuit on the low tension side.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: RichardL on 16.07. 2014 23:45
Beezermacc (Andrew?),

Thanks for the thoughts. I believe the cam ring had floated completely off the stop pin. Until Groily shared the secret with me, I had no idea the pin was eccentric. When I first checked it, hardly any bump was available to engage the ring. In addtion to having no o-ring in the cover, I had been kicking the bike over and even started it once with the cover off. Now, I've set the pin position for no (or, bare minimum) cam ring slack. I've yet to get her back together, but I'm feeling somewhat confident that this may well have been the problem. However, it seems confidence is a setup for let down. I hope it isn't intermittance, since that is usually hard to pinpoint. I'll keep the forum posted on results.

Richard L.

Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: beezermacc on 18.07. 2014 06:35
You could drill the cam ring housing 180 degrees from the existing peg, tap the hole maybe 3mm and fit a screw to act as a new peg then fit your cam ring 180 degrees from its original postion. If you mark the cam housing with the position of the lift on the cam ring before removing it you can be sure of drilling in the right place for your new peg. The old peg can be removed and the hole plugged or just grind the peg away.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: RichardL on 18.07. 2014 08:14
Thanks, Andrew. I think the original eccentric stop pin should work now, now that I know it is an eccentric stop pin. Just wondering, would it make a wit of difference where the cam ring was rotated to in an automatic advance machine? It seems not. but as always, I'm pro at missing something.

Richard L.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: Triton Thrasher on 18.07. 2014 20:36
The eccentric pin is used to keep the cam ring in such a place that the points open at the ideal armature/magnet relative position for strongest spark.

Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: RichardL on 18.07. 2014 21:11
That makes perfect sense TT, thanks. Now, I am still assuming that 180 deg. rotation  of the cam housing doesn't matter. My eccentric pin was at the bottom and unadjustable.

Richard L.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: RichardL on 18.07. 2014 21:56
Also, would suggest you make up a gasket or seal thick enough for the end cover of the cb housing to pinch against the camring, to stop it fretting if it's so inclined. Often, the seals supplied or fitted don't actually engage the camring at all.

Bill, et al,

So, looking at the fit of the cam ring versus the bakelite end cap, it appears that the o-ring (which is missing from mine) only serves as a dust and water blocker. The cam ring then appears to be held into the housing by three shoulders formed within the cap inside the inner diameter of the o-ring groove.  It then seems possible that if you use too thick an o-ring you space the hold-down shoulders away from the cam-ring, maybe making a problem if your eccentric is not protruding (hmmm, that's one way of saying it).

Richard L.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: groily on 18.07. 2014 22:49
With the plastic covers Richard (as opposed to alloy domes or screw-on types), there's always going to be a question about the strength of the clip that holds it on - whatever else you do. I guess the best you can do is make sure the plastic feet and/or the rubber or other seal don't leave a gap  . . .  Hard to see I know, when the end cover is on, and against the slight pressure of the kill button strip as well. If you've now got your camring pegged in place (whichever way round) then it shouldn't rotate in ways you don't want, and it shouldn't move axially if there's any sort of contact keeping the darn thing in place. Assuming these things are OK, you can then start to discover whether you get those errant sparks back  . . . fingers crossed.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: duTch on 19.07. 2014 00:11



Not sure if I read that wrong, or you didn't write what you were thinking....or...?

 Maybe you can rotate the whole housing as a unit, but with no net advantage, ?...(on mine the two opposing interface screws are different sizes)

  The camring being symetrical, disregarding locating pins, can be rotated exactly 180˚ for same net result, and hypothetically without any rotation, you could make a new locating slot wherever you desire, with corresponding pin- but why.... if you can just rotate it if need be and relocate the pin.

 I think, as it was running ok before (original bike? not new project?), it should in theory be ok, and you may hopefully be addressing a non existent or incorrect issue, or agonizing unnecessarily...?

 either way I hope you get it sorted... *beer*
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: RichardL on 19.07. 2014 05:39
Dutch,

You gave me a scare when you said the screws might be different sizes. Mine are not (see photo showing the two from my second mag). In my case, the net advantage is having access to the cam ring stop pin, rather than having it completely inaccessible on the underside of the mag. As far as I can tell, no need for me to add a different stop pin location or an additional slot in the ring.

Richard L.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: duTch on 19.07. 2014 09:36

 Yep, ok sorry didn't mean to do that-  *smile*
 I'd say mine are maybe 1/4 & 3/16, but keeping in mind mine's an earlier(circa '50) maggie as determined a while ago by Trev. I think...

 maybe post a pic of the overall offending area so we can all have a nitpick. *smile*....no I really just mean to get it in perspective, particularly for future enquirers *smile*
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: beezermacc on 30.07. 2014 12:32
The threads of the screws which hold the cam ring housing on a K2F are 2BA, and 1/4 whitworth on a K2FC.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: RichardL on 30.07. 2014 13:15
Andrew,

Hmmm. So, because Dutch's housing screws are two different sizes, maybe one hole in his mag was stripped and repaired at 1/4". That would imply that he has a K2F.

You must have been back-reading a lot of posts to dredge up this topic. It pains me to say that work deadlines (those already missed and those forthcoming) have kept me from working on the bike since discovering the loose cam ring. All I can say is that I hope winter comes late in Chicago.

Richard L.
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: duTch on 31.07. 2014 00:17

 Ok Richard, you better dig out that green 'cone of silence'- when I read your post last night, I realized I was talking about the outer cover, threads I measured up as 0.1830" & 0.2365"- don't have a BA gauge, but as far as I can determine are 2BA & 0BA respectively, with the inner cover screw(1 of in pic), being also 2BA. *red*- will match the green hat *smile*
 0BA 25.4 tpi, close as to 1.0mm
 2BA 31.4 tpi, close as to 32 tpi

 As an aside, I'm curious how the BA pitch is calculated, as the only pitch with an even number- no decimals- is 5BA 0.126"@ 43tpi, kind of wonder if it's somehow based on a metric scheme or other??
 I guess I could do a web search, maybe later.....
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: morris on 31.07. 2014 17:36
I guess I could do a web search, maybe later.....

Have a look here Dutch. Helped me out a few times already;

http://www.britishfasteners.com/threads/index.html

And if you understand the explanation of how it's calculated, then please explain it to me in normal language *countdown*
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: duTch on 31.07. 2014 22:12

 Thanks Morris- I think *eek*. I'll check it out later
Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: RichardL on 15.09. 2014 22:55
Hi guys,

 I want to close off this story before moving to the next. Besides, I feel like I owe it to you after getting good advice. About three weeks ago I had a fairly detailed story written out on my iPad (don't blame me, family decided it was a good gift for a milestone birthday). That story disappeared with an errant screen touch, so you may consider yourselves lucky to be spared even more tedious detail than I give here. So, I'm going to try to do it in shorthand so I can move on to my latest issues.

After all-winter engine rebuild, started once or twice, then: no start. So, struggle, time, kick, struggle, time, kick, etc, etc. etc.

Replace plugs wires and caps with great quality parts, re-time, starts a couple of times on first kick, put everything back together, then: no start. So, struggle, time, kick, struggle, time, kick, etc, etc. etc.

Discover lock pin not keeping cam ring in place. To access lock-pin adjuster, decide to rotate cam-ring housing 180 deg. Easy to do. Re-time. No start. So, struggle, time, kick, struggle, time, kick, etc, etc. etc.

Comb cobwebs of mind to recall the need to check point gap for each lobe. Gack! Rotating the housing led to the cam ring being well off center. Removed the mag, rotated housing back the way it was, gapped points for both lobes. Turned out very close. Reinstalled mag (duh, but thought I was on Candid Camera while trying to reinstall the long nut). Timed. Success! Put everything back together. Still success. Starting regularly on three or fewer kicks, often, one.

All of the above covering about three months, what with other things going on in my life and a limited amount of knee cartilage available to contribute to the cause at any one time.

With the rebuild running apparently fantastic, put about 200 miles on her before doing something I had not done before, specifically, get on the open highway and run her fast, briefly up to about 80 MPH (I know, not fast compared to racers here). Well, something happened. Now, if you want to read more, head over to my "Piston Melted?" topic in the "Engines" section.

Richard L.



Title: Re: Magneto bad all of a sudden, and then, only sometimes?
Post by: duTch on 16.09. 2014 10:13

.....yup......