The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: BSA59 on 11.02. 2007 12:39

Title: BSA A10 ignition
Post by: BSA59 on 11.02. 2007 12:39
Hello,I'm sorry I live in France and i don't speak english very well
I want to know the ignition advance for my BSA A 10 Road rocket of 56
I need this information but not in inch but in degrees
I hope you understand me
Thank You!
good afternoon
Fred
Title: Re: BSA A10 ignition
Post by: a10gf on 11.02. 2007 18:45
Bonjour, et soyez le bienvenu ici. N'ayez pas de doute, votre anglais est très bon, et ne posera aucun problême. Maintenant la France est representée sur le forum, excellent!
Moi, j'ai passé beaucoup d'années en France, banlieue de Paris et les Alpes Maritimes. Dans quel département habitez vous?
e.

ps, we will keep the forum in english, this is just a welcome note to our new french member.
Title: Re: bsa A10 IGNITION
Post by: dpaddock on 16.02. 2007 00:51
Fred: Try 32 degrees BTC, equivalant to 5/16-inch.
Title: Re: BSA A10 ignition
Post by: BSA59 on 17.02. 2007 16:44
Hello
to a10gf: thank you for your welcome note,I'm living near Valenciennes- I have a recent bike(TRIUMPH TBIRD BIRD) and old bikes (SAROLEA 30R, NSu 200lux,MOTOBECANE R 44 C,BSA M20...)
to dpaddock: thank you for your information
Fred
Title: Re: BSA A10 ignition
Post by: a10gf on 18.02. 2007 11:02
Some GF timing I picked up somewhere, think it was recommended by SRM using their timing disc:

35 deg btdc for super98
33 deg btdc for 95

Fred, post a few pictures of your bikes? (other than a10 pics welcome as well, especially BSA's, as long as you own an A10 too, BTW, I have a Triumph 900 Legend, good stuff ! )

e.
Title: Re: BSA A10 ignition
Post by: Beezageezauk on 18.02. 2007 14:40
Hi Fred,  

Welcome to our BSA A7/A10 forum and congratulations on your English.  We can understand you very well.

I have just done some calculations using the Ignition Timing Converter and these are the results.

Using the A10 stroke of 84mm....3.307 inches and the conrod centre distance of 6.469 inches the ignition timing conversions are as follows.

5/16in. before top dead centre is 0.3125inches or 32.5deg.
11/32in. btdc is 0.344inches or 34deg.
3/8in. btdc is 0.375inches or 35.5deg.
13/32in. btdc is 0.406inches or 35.5deg.

You decide what your ignition timing should be  *doh* in inches before top dead centre and the answer you are looking for is here.

Beezageezauk.
Title: Re: BSA A10 ignition
Post by: Alan @Ncl on 22.01. 2011 11:38
I just came across the post quoted below and realised I was probably using the wrong data in my calculation (posted yesterday and now corrected).  Can I just seek confirmation of consensus that A10 con-rod length between centres is in fact 6.469inches (I was using 6 inches which obviously gives a slightly different answer).

Also, can anyone say how many degrees the autoadvance mechanism normally provides?  I did some measurements (gap to be taken up by the centrifugal action, about 6mm, and the diameter across yoke about 60mm).  This indicated an equivalent of about 23 crankshaft degrees.  On this basis, fully retarded would be about 12 degrees BTDC.  Does that sound sensible? I seem to recall seeing somewhere that it was nearer TDC.

I have just done some calculations using the Ignition Timing Converter and these are the results.

Using the A10 stroke of 84mm....3.307 inches and the conrod centre distance of 6.469 inches the ignition timing conversions are as follows.

5/16in. before top dead centre is 0.3125inches or 32.5deg.
11/32in. btdc is 0.344inches or 34deg.
3/8in. btdc is 0.375inches or 35.5deg.
13/32in. btdc is 0.406inches or 35.5deg.

Beezageezauk.
Title: Re: BSA A10 ignition
Post by: KeithJ on 05.08. 2013 11:51
Hi, I have just checked my A/R unit on my A10RR and it has 12 deg of movementwhich agrees with the above post.  However, I think it should be more than this. Is there a difinitive figure for this taking in to account the modern fuels?  Also, what degree of retard should there be with, say 8:1 pistons to ensure easy starting and correct advance?  Hope this is clear?  ATB
Title: Re: BSA A10 ignition
Post by: KenF on 05.08. 2013 12:38
Keith, the spec for the ATD range on 1955-57 A10RRs was 11 to 13 degrees, and I doubt if they would have changed it by 1959. See page G22 of
http://brightsparkmagnetos.com/library/Parts%20lists/Lucas%20motor%20cycle%20parts%201936-57/G09-23%20Magnetos%20and%20ATDs.pdf (http://brightsparkmagnetos.com/library/Parts%20lists/Lucas%20motor%20cycle%20parts%201936-57/G09-23%20Magnetos%20and%20ATDs.pdf)
So, your 12 degrees sounds good to me. Bear in mind that that equates to 24 degrees of advance/retard at the crankshaft.

I can't say anything definitive about modern fuels and 8:1 pistons, other than I wouldn't worry about it.

Cheers,
Ken
brightsparkmagnetos.com (http://brightsparkmagnetos.com)
Title: Re: BSA A10 ignition
Post by: KeithJ on 06.08. 2013 13:52
Thanks for the posts.  Why would SRM give 35 & 33 Deg?
"Some GF timing I picked up somewhere, think it was recommended by SRM using their timing disc: 35 deg btdc for super98
33 deg btdc for 95"

Sounds quite different to 24 Deg with a std A/R unit?

So if the ignition is set at 33 deg BTDC and there is 24 degrees of advance, does that mean static timing at tickover will be 9 deg BTDC?  Surely, it will need to be set up to start with much less than 9 deg BTDC?

If the standard A/R unit is used with 12 deg (24 crankshaft), then with say 2 deg BTDC at "rest", there is only about 22 deg of advance.  What have i missed?

Keith


Title: Re: BSA A10 ignition
Post by: muskrat on 06.08. 2013 14:34
10 degrees BTDC at idle sounds about right Keith
Cheers
Title: Re: BSA A10 ignition
Post by: Retired Fireman on 19.08. 2013 01:24
Comfirm what Muski said, I had to modify my A10's mag as it had a Triumph advance unit (15-18deg) unit that someone put a BSA pinion on and the advance range was too much. Idled at TDC then advanced to 33 deg, now it idles at 6deg and advances to 33, this transformed the performance and idle of the bike as the advance curve now seems correct for the given RPM of the engine. The note of the engine at idle always sounded flat before I discovered this and it was unstable when hot at idle, when experimenting I set the timing at 10 BTDC and the idle was perfect but after checking with a strobe light after modifying the ears on the auto unit it worked out to 6deg idle and 33 fully advanced and it runs stronger than it ever did. Of course don't forget the mag degrees are half of what the crank degrees will be. *smile*
Title: Re: BSA A10 ignition
Post by: muskrat on 19.08. 2013 01:58
G'day Arthur, long time no see here.
At zero BTDC it will start easy and idle when cold but as Retired Fireman found not good when hot (or even warm).
Cheers
Title: Re: BSA A10 ignition
Post by: KeithJ on 28.08. 2013 08:24
Some GF timing I picked up somewhere, think it was recommended by SRM using their timing disc:

35 deg btdc for super98
33 deg btdc for 95

Fred, post a few pictures of your bikes? (other than a10 pics welcome as well, especially BSA's, as long as you own an A10 too, BTW, I have a Triumph 900 Legend, good stuff ! )

e.
Just took this from the SRM web site
http://www.srmclassicbikes.com/technical/timing-figures
BSA A7/A10
A7.  Alloy Head: 35 degrees (5/16th) (btdc)
A10, Iron Head: 33 degrees (9/32) (btdc)
A10, Alloy Head: 35 degrees (5/16th) (btdc)
 
ATB

KeithJ
Title: Re: BSA A10 ignition
Post by: orabanda on 28.08. 2013 10:48
I find the best results are when the timing is retarded 3 degrees on the commonly published figures: ie 32 degrees BTDC for alloy heads, and 30 degrees for iron heads. More HP, torque, and less pinging.

Richard
Title: Re: BSA A10 ignition
Post by: KeithJ on 28.08. 2013 15:06
Interesting posts.  Looks like for my ally head A10 I will use 32/33 BTDC and the 24 Deg of advance will end up with 8/9 Deg at idle.  
What governs the Idle advance apart from the movement on the advance and retard unit?  I am tying to understand if it is worth fine tuning the A/R unit or is it just not that critical?
If it is not that critical, why the issue with the greater advance on using a Triumph A/R unit
ATB
KeithJ
Title: Re: BSA A10 ignition
Post by: RichardL on 28.08. 2013 21:21
Reading all this is interesting, though, less useful to us folks just dipping a measuring device into the plug hole. Still, good stuff. Speaking of the auto advance mechanism, I'm into my timing case for a dynamo belt conversion and checked my home-made auto-advance return springs. Still good after about 3,500 miles.

So, I wonder what the heck happened to Fred in France, who started this phread (uh, "thread") in '07?

Richard L.
Title: Re: BSA A10 ignition
Post by: Retired Fireman on 29.08. 2013 23:19
Keith J,
         What was happening with my engine was because the range of advance was set for a Triumph which the timing is 38 deg fully advanced the A/A unit (Auto Timing Device) advances from around 6-8 deg at idle to 38deg fully advanced (around 15-18 deg at the magneto) but when this unit is fitted to an A10 the timing is set to 32-33 deg fully advanced then the timing would retard to around TDC. A10's need around 11-12 deg (magneto) of advance so the timing was over retarding back to TDC instead of around 8-10 (crankshaft) that they need to idle properly, also the timing advance curve would be retarded through the advance range until near 3000rpm where it became fully advanced. My A10 started and idled good when cold but when warmed up the idle became unstable, as well the engine was lacking performance because the advance curve was retarded. After modifying the advance range in my ATD the engine was transformed and now idles with complete reliability in traffic when hot and runs very strong. If you choose to time your engine useing the broomstick down the plug hole method you don't know if the advance curve is correct and if it is over retarding back to idle or whatever. SRM sell a "strobe timing kit" which consists of a new crank spring nut machined to accept the alloy timing disk they supply Then all you do is remove the primary cover fit the disk to the crank nut with 2 allen screws supplied, find TDC (piston stop method is best to accurately do this) attach a strobe light with an external battery, clip onto either side spark plug wires and you can watch your advance curve happen and properly time you engine for optional performance plus check the timing between cylinders and if needs it adjust it in your mag. Hope this explains the importance of the correct ATD being fitted to your bike.
Title: Re: BSA A10 ignition
Post by: KeithJ on 30.08. 2013 08:33
Appreciate your reply Retired Fireman.  Essentially, the difference between the two ATD's is the Triumph one gives about 5 Deg at tick over and the BSA one 10 Deg.  Also, this difference retards the advance curve.  Brilliant.  Apart from "Fully Advanced at 3000 RPM" what are other "typical" advances at say, 1000, and 2000 RPM?  With these additional key advances, it will be possible to confirm the correct springs are on the ATD?
ATB  KeithJ
Title: Re: BSA A10 ignition
Post by: Retired Fireman on 31.08. 2013 00:35
Hi Keith, I cannot confirm actual BSA timing advance curve specs for A10's in advance to RPM steps someone here might know? In their day BSA didn't publish a lot of detailed info to the public they just gave a limited amount to dealers so they could make money out of us if we where not smart enough to figure this sort of stuff out ourselves. By me building up the retard side of the ATD 's lug or ear to limit the amount of advance I essenually tightned the advance springs as you can imagine, as long as the advance is all in (fully advanced) at around 3000RPM the curve wouldn't be too far wrong I think, if on the other hand the springs are too weak the advance would be all in before 3000 and essrentually over advanced too early in the RPM range that could cause pinging and possible over heating if you rode in that RPM range for a while. If someone on here has a 6v Boyer electronic conversion they could set up a degree disc and timing light and record what figures the boyer gives at 1000-1500-2000-2500 etc and share this with the forum. My advance curve is nice and even to about 2000 then it slows down to be all in at about 3000. P.S. my bike is an iron head A10 7.25 to 1 comp, 356 cam with late model flash biger port head and air filter running on 95 fuel, alloy heads with higher comp and 357 cam timing would I think be different so don't take my specs as across the board
Title: Re: BSA A10 ignition
Post by: KeithJ on 31.08. 2013 08:12
Thanks for the post Retired Fireman.  Hope someone can post the advance curve details.  Returned from a run on my A10 and as the engine slowed and stopped when I got home, a strange tinkling sound came from the engine.  Have checked it and it looks like something significant has gone wrong inside the engine. Perhaps and end.  Ah well!!!!!!!
ATB
Title: Re: BSA A10 ignition
Post by: muskrat on 31.08. 2013 08:57
Hopefully just the fins saying they've had fun (got good and hot). How far and hard was the run?
Cheers
Title: Re: BSA A10 ignition
Post by: Retired Fireman on 31.08. 2013 10:59
Did the "tinkling sound" occure as the engine wound down, it could have "run on" a couple of revs because the plugs were overheated. Before the doom and gloom starts whip out the plugs and have a look at the electrodes to see if there is any sign of overheating on their tips, your ignition timing might be a little advanced or you have fitted the wrong heat range of plugs. In my iron head A10 I run NGK --7ES (I'm at work and nearly finished a 12 hr shift and can't think it could be BE) If you have an alloy head check the correct heat range you have fitted and of course the gap is correct. By the way SRM recommed 35 degrees for alloy heads and 33 degs for cast iron according to their website. Let us know if you find out what the "tinkling sound" was, I will be away from the Forum for 2 weeks as I am riding my 57 A10 up to the Queensland BSA club's "All British Rally" near kingaroy in Qld then returning via a few friends homes about 3000 k'm so will blow the cobwebs out of the old girl. Will check on your progress on return good luck!
Title: Re: BSA A10 ignition
Post by: Retired Fireman on 31.08. 2013 11:14
Just another thought: have you had your ignition checked with a strobe light on BOTH plugs? I have seen 5 degrees plus variance between the two cylinders and if you have set your ignition on one side and not checked the other, the cylinder on the other side could be 38 BTDC and the one you timed it on would be 33, that would heat up the other plug and possibly cause the "running on" that is the tinkling sound when the engine stopped. Or maybe not (GULP!)
Title: Re: BSA A10 ignition
Post by: KeithJ on 31.08. 2013 11:30
Have a good run.  Sounds like a lot of fun.  Be interested to hear how the run went, weather and all.  Bikes been running OK for years.  Plugs look fine, still makes the sound just turning it over on the kick start.  Will be a few weeks before I get to look at it further but will let you know what I find out.  Due end of September to collect another bottom end, roller conversion, cases, new rods and pistons etc so aim to rebuild that.  Will check timing on both cylinders.  Good point.  Will get the old girl re-painted as she is in need of it. ATB
Title: Re: BSA A10 ignition
Post by: muskrat on 31.08. 2013 21:22
Ah, the sound you hear when winding the motor over is the backlash in the timing gears. At one point in the revolution the valve spring pressure tries to push the cam backwards and reverses any play in the gears. Sort of a clinking sound.
I agree with RF that it might be running on when you turn it off, and you would hear the above sound as well as piston knock. If it's caused by incorrect or uneven timing a new SRM bottom end won't fix it.
Cheers
Title: Re: BSA A10 ignition
Post by: Retired Fireman on 01.09. 2013 05:36
As Mr muski sezz it could be the clearence between the immediate, main pinion and cam gears causing the racket, throw in wear in the intermediate gear bushes in the inner case and crankcases plus a bit of wear in the camshaft bushes and you would have a synphany of clickingness as the camfollowers change the direction of thrust on the gear stack clearence as each cam goes over the top ramp of it's cam lobe. Triumph twins suffer badly from this because they have two camshafts and the gears were individually selected when new to run quietly together but along the way they either wear or get subsituted with timing gears that don't match. BTW if you are forking out for a roller bearing conversion and new everthing have a look at the SRM timing kit with spring crank nut so you can accuratly time the engine and check advance curves as well as timing between cylinders, but before you do be EXTREMELY carefull establishing TDC when setting up the pointer on the disc, don't forget as the piston stops momentarly at the top of the stroke the crankshaft is still moving and it takes very little movement to give a few degrees either way in crank movement. An excellent discription and a few methods on how to establish acurate TDC is on a car engine site "ISKY CAMS" it explains how to do it dead acurate and how to check your TDC with a degree disc and the "piston stop method" I turned up an adjustable "piston stop" that screws down my drive side plug hole and locks the piston in 33 deg before TDC, I carry it in my tool kit so at anytime in the field I can quickly and dead accurately put my engine in 33 deg BTDC for checking timing as well as establishing a pointer at TDC. Hope all this info helps.
Title: Re: BSA A10 ignition
Post by: KeithJ on 01.09. 2013 09:41
Constructive posts, thanks.  Noise I have is the same as taping a cylinder fin.  A clear bright sound. Interesting to me it happened just as I got home.  I'd switched of the petrol and was just running the carb dry.  Perhaps just coincidence.  I will find out when I look further in to it.  The new roller bottom end is in another set of cases.  It was already underway and not being done to sort out this problem.    ATB
Title: Re: BSA A10 ignition
Post by: duTch on 02.03. 2014 01:38

 I was searching for 'ignition related' and found this maybe should do a new post, however...??

 
Quote
a strange tinkling sound came from the engine.

  Ok Tinkerbell (Keith J)...don't do a 'Phread' on us and keep us 'Guesting'......I just read through this whole phread, and don't know what was the 'tinkling'... *????*
Maybe it's in another 'Fread'?

 Generally I do the measuring stick down the hole, but while replacing my cush drive spring the other day, I made a rudimentary degree wheel from a plastic container lid to screw onto the crank end (see photo), and roughly checked my timing which was about  ~20˚, so with a bit of play in the CB plate key, moved it ~10˚ to ~30˚ btdc was running fine before with only a bit of occasional miss, and seemed fine when I set off for test ride yesterday, as usual starts first kick, got about a mile up the road and setting off from lights, went into splutter mode and conked out- started after a bit but only another block and stopped completely, played with plugs and usual stuff- pushed home, had beer, and still no (very minimal) spark/no go.

 Finger-in-pickup-hole-spark-detector- nothing much....*eek*

Checked and cleaned Earth brush and slipring and other brushes, one behind CB plate had grease on, after which managed to achieve a splutter or two

 Maggie rebuilt in late nineties by (legendary) Les McKitterick, who assured me it will outlast me.. *conf*, before sitting till a year ago and  has only done ~3000 miles since.

  Found the 'points retaining clip' broken and missing, (see other photo) is this otherwise important, and, if it was flapping around in the housing- is there likelihood of shorting or de-magetizing anything...???

 Any other clues I haven't thought of, maybe condenser which I'm sure he replaced....maybe need a brightspark??

 Cheers in advance, that was epic- need refreshment!

Title: Re: BSA A10 ignition
Post by: duTch on 02.03. 2014 10:52

 Ok, I may have jumped the gun a bit (all three of 'em)....after playing and cleaning and measuring bits and ohms, threw it back together this morning, and first kick away she goes... *good3*..... *dunno*
 Did a bit of a lap of the old block ~about 20 miles- seems ok, pops and splutters a bit here and there, but running as well as it did before so will just continue as per usual...see what happens tomorrow if I don't get scammed into workin'
Title: Re: BSA A10 ignition
Post by: KeithJ on 21.07. 2020 20:47
Doesn't time fly.  Recently having some mag issues and came across Runtronic CDI ignition as a possible replacement for my mag.  Started to look at timing curves, ATD advance and static timing.  Found it had been covered before for different reasons but just slipped my mind.  This has made interesting re-reading and shown how valuable the search facility is.  Excellent source of information.
Thanks to everyone who posted.
Title: Re: BSA A10 ignition
Post by: muskrat on 21.07. 2020 21:01
G'day Keith.
One day I'd like to try the Dyna 2000ip in the Cafe. It is fully programmable with 4 advance curves but can program my own curve with the laptop, rev limiter (I need that!) and records all the info for download.
Cheers
Title: Re: BSA A10 ignition
Post by: KeithJ on 21.07. 2020 21:08
G'day Keith.
One day I'd like to try the Dyna 2000ip in the Cafe. It is fully programmable with 4 advance curves but can program my own curve with the laptop, rev limiter (I need that!) and records all the info for download.
Cheers
Oooch! That sound like Rocket Science to me. Just want something which simple, reliable uses veery little electricity and little space.  Looks interesting http://www.jeperformance.biz?  I think I am an analogue guy in a digital world!

Title: Re: BSA A10 ignition
Post by: muskrat on 21.07. 2020 21:31
G'day Keith.
Yes the Runtronic sounds great for a std or close to bike.
I need a bit more on the Cafe as with the Boyer that's on it I still get pinging under hard acceleration (every time I ride LOL). If I retard enough to eliminate the pinging the performance drops considerably and she overheats.
On the A7 plunger the Boyer is great.
The Dyna 2Ki is designed for HD's but I could adapt. I put one on a mates Evo and was amazed at the performance. http://www.dynaonline.com/products/harley-davidson/dyna-2ki.aspx
Cheers 
Title: Re: BSA A10 ignition
Post by: beezermacc on 22.07. 2020 07:58
 
Cheers
[/quote]
Oooch! That sound like Rocket Science to me. Just want something which simple, reliable uses veery little electricity and little space. 
[/quote]
…. a magneto maybe?
Title: Re: BSA A10 ignition
Post by: KeithJ on 22.07. 2020 08:16

Cheers
Oooch! That sound like Rocket Science to me. Just want something which simple, reliable uses veery little electricity and little space. 
[/quote]
…. a magneto maybe?
[/quote]
Excellent observation.  Even simple things are complicated if not under stood or familiar enough with them.  Would be simpler if there was consensus about solving a specific issue but that rarely happens.   Hey ho!  Now to sort out clutch slip.  Off to read those threads.  Original clutch worked well for years but SRM one hasn’t.  Progress? 
Title: Re: BSA A10 ignition
Post by: BSA_54A10 on 22.07. 2020 09:06
Just a little word of warning if fitting a Runtronics.
It throws a cluster spark which means that no matter what the cylinder is going to fire.
A customer fitted one to his T100 and found it to be overheating due to running lean.
HE also found a big increase in Hp to the point that the clutch could not cope.
Now this was not a std bike as he was into Vintage Moto Cross & Trials so lots of revs with little cooling breeze
HE converted about a dozen more and the singles did not seem to have the same problem but he went up a jet size or two right from the start.
There is a mounting package offerred by a different mob for the Runtronics specifically for British alternator bikes ( natually no longer fitted ) which had both a arc and a radial slot for adjustments .
What people forget when they fit them is positioning the sensor closer to the magnets also advances the timing so you need to be able to rotate as well as alter the radial space.
FWIW he used 5 NiCd C cells to power the Runtronics which gave around 17 hours running time
Title: Re: BSA A10 ignition
Post by: KeithJ on 22.07. 2020 10:36
Just a little word of warning if fitting a Runtronics.
It throws a cluster spark which means that no matter what the cylinder is going to fire.
A customer fitted one to his T100 and found it to be overheating due to running lean.
HE also found a big increase in Hp to the point that the clutch could not cope.
Now this was not a std bike as he was into Vintage Moto Cross & Trials so lots of revs with little cooling breeze
HE converted about a dozen more and the singles did not seem to have the same problem but he went up a jet size or two right from the start.
There is a mounting package offerred by a different mob for the Runtronics specifically for British alternator bikes ( natually no longer fitted ) which had both a arc and a radial slot for adjustments .
What people forget when they fit them is positioning the sensor closer to the magnets also advances the timing so you need to be able to rotate as well as alter the radial space.
FWIW he used 5 NiCd C cells to power the Runtronics which gave around 17 hours running time
Interesting and appreciate the post.  Lots to consider before going that route.  What is the difference between "cluster of sparks" and "wasted sparks"?  I understand Runtronic gives multiple sparks at "tickover" and thought used wasted spark through the rest of the range.  Sounds like changing one set of problems for another?  Also, I have not been able to clarify what the advance curve is. 
Title: Re: BSA A10 ignition
Post by: muskrat on 22.07. 2020 10:46
G'day Keith.
Wasted park means it sparks on the exhaust stroke as well. Most if not all electronic ignitions on twins and fours do this.
Cheers
Title: Re: BSA A10 ignition
Post by: KeithJ on 22.07. 2020 11:07
G'day Keith.
Wasted park means it sparks on the exhaust stroke as well. Most if not all electronic ignitions on twins and fours do this.
Cheers
That's what I thought.  I didn't understand if  "cluster" meant the same.  Thanks
Title: Re: BSA A10 ignition
Post by: BSA_54A10 on 23.07. 2020 09:43
It meas exactly what it says. you get several sparks one after another.
It was designed for model aircraft where the cylinder has to fire every time without fail
So you get a rapid group of sparks rather than a single one.
Drove the induction tacho crazy
Title: Re: BSA A10 ignition
Post by: KeithJ on 23.07. 2020 15:22
Just a little word of warning if fitting a Runtronics.
It throws a cluster spark which means that no matter what the cylinder is going to fire.
A customer fitted one to his T100 and found it to be overheating due to running lean.
HE also found a big increase in Hp to the point that the clutch could not cope.
Now this was not a std bike as he was into Vintage Moto Cross & Trials so lots of revs with little cooling breeze
HE converted about a dozen more and the singles did not seem to have the same problem but he went up a jet size or two right from the start.
There is a mounting package offerred by a different mob for the Runtronics specifically for British alternator bikes ( natually no longer fitted ) which had both a arc and a radial slot for adjustments .
What people forget when they fit them is positioning the sensor closer to the magnets also advances the timing so you need to be able to rotate as well as alter the radial space.
FWIW he used 5 NiCd C cells to power the Runtronics which gave around 17 hours running time
"HE also found a big increase in Hp to the point that the clutch could not cope."  That sounds a very effective way of tuning.  How does that happen?
Title: Re: BSA A10 ignition
Post by: edboy on 23.07. 2020 21:46
interestingly some single prop aeroplanes have a shower of sparks mag for easy starting. unfortunately its only one mag and if that fails the other mag will not start the plane and the right type of mag has to be ordered. catches owners  and techs out.
Title: Re: BSA A10 ignition
Post by: KeithJ on 24.07. 2020 18:38
Just reduced the plug gap on my SR to 0.012".  Why does it take less of a swing on the kick start to start it?  Does that indicate a mag isn't working as it should?
Title: Re: BSA A10 ignition
Post by: Triton Thrasher on 24.07. 2020 19:36
  Does that indicate a mag isn't working as it should?

It indicates that something isn’t at its best,  but if you’re getting by with a small plug gap, you’re getting by.
Title: Re: BSA A10 ignition
Post by: RDfella on 24.07. 2020 20:00
I wonder how many simply put plugs in without checking the gap? On cars, always used to be .025" and most plugs came pre-gapped to that. But nowadays, with electronic ignition, some plug gaps are 1mm or more (.040" +). Not with old magneto-ignited bikes. I believe the recommended gap was .017" - at least that's what I've always used.
Title: Re: BSA A10 ignition
Post by: KeithJ on 10.08. 2020 18:54
Just dropped my plug gap to 0.010" and is easier to start.  Also starts more consistently on the electric starter.

If having a cluster of sparks increases power output significantly, what performance is lost, if any, by reducing the plug gap by about 50% on a mag?

Title: Re: BSA A10 ignition
Post by: RDfella on 10.08. 2020 19:34
I would doubt a cluster of sparks would increase power by a measurable amount, never mind significantly. Might ensure more complete combustion with today's weak mixtures (which I believe was the purpose) but unless the combustion chamber is an awful design, can't see what difference it'd make with normal fuel / air ratio. As for reduced spark gap for magnetos, it may slightly reduce performance, but then if you can't start it there's zero performance. Again, I believe the purpose was to ensure a more reliable start, given a magneto's weak spark, especially at kick-starting revs.
Title: Re: BSA A10 ignition
Post by: KeithJ on 10.08. 2020 21:16
I would doubt a cluster of sparks would increase power by a measurable amount, never mind significantly. Might ensure more complete combustion with today's weak mixtures (which I believe was the purpose) but unless the combustion chamber is an awful design, can't see what difference it'd make with normal fuel / air ratio. As for reduced spark gap for magnetos, it may slightly reduce performance, but then if you can't start it there's zero performance. Again, I believe the purpose was to ensure a more reliable start, given a magneto's weak spark, especially at kick-starting revs.

Just going on from what  BSA_54A10 said on an earlier post:

A customer fitted one to his T100 and found it to be overheating due to running lean.
HE also found a big increase in Hp to the point that the clutch could not cope.
Now this was not a std bike as he was into Vintage Moto Cross & Trials so lots of revs with little cooling breeze
HE converted about a dozen more and the singles did not seem to have the same problem but he went up a jet size or two right from the start.

So still don't understand?


Title: Re: BSA A10 ignition
Post by: RDfella on 10.08. 2020 22:01
Yup, I understand science. Does anyone have the data and test figures to back up this power increase assertion?