Boyer Mark III vs Mark IV

Is there any difference in the advance curves?
I think need a curve that starts with less advance than my current MK III during the kickstart routine. My ankle is killing me after a vicious kickback today, and I cannot afford to be crippled or afraid to start the machine, either.
I found advance curves for almost everything except the Mark IV, which does claim to have improved it's sensitivity to low voltage.

I would think the problem may lie in the initial advance setting as there should be no advance until it's running.

I think the problem may not be the curve or the initial setting, but possibly the power supply to the Boyer.

Low volts cause a MK3 to go fully advanced, charge your battery before starting or go MK4 which does not have this issue.

Mr. Rick said:

I found advance curves for almost everything except the Mark IV, which does claim to have improved it's sensitivity to low voltage.

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Can you confirm it had been set accurately (with a strobe)?
Was the battery less than fully charged?

As mentioned, the problem with the old Boyer MkIII is that the 'advance' (retard) becomes increasingly erratic due to low voltage and not necessarily because the advance curve is wrong.

http://atlanticgreen.com/boyerevolved.htm
"Boyer MK III (analog)
Voltage Duress induced Spark Jitter"

Mr. R. .... as far as info above I think it right on .... several years ago had to repair my original Boyer the wire on pickup had cracked ... repair last a few years then I assume it failed right at my handiwork .... so installed the new improved at the time Mk IV ... since then I have had zero kick back ... granted bike is kept on maintainer when not being ridden , but it was same when old Boyer was in use .... an added benefit seems like my battery is lasting longer , in fact I replaced it at the time of MkIV and battery is still strong .... it has been a couple of whiles since the install , I would strongly recommend upgrading to the MkIV ... no more sore ankles , calfs , etc. just nice consistent starting and running ...
Craig

Boyer's advance curve sucks. The fact that they want you to set the timing ay 5k RPM tells you all you need to know. The advance should be all in by 3k RPM. The stock system does that. Any system that doesn't is reducing your low/mid-range power.

Sad but true , only set time by feel , advanced till kickback then back couple degrees ... bike has no lack of performance anywhere in rev range ... or more precisely my own safe rev limit .... still running with original bottom end .... Combat rarely take it past 5000rpm with the 21T countershaft sprocket , that plenty for this old man ...+ 80mph
Craig

Today my pal Clay surprised me with a visit, and as soon as I fixed him a cup of coffee, I put him to work on the throttle so I cd take strobe readings at various RPM levels.
BTW, the battery is new and was fully charged. Kicked it with all the gusto I cd summon while praying for my ankle, still sore from yesterday, and it fired.
I had printed out the chart found here: http://www.nocnsw.org.au/technical/ignition-timing-for-commando-boyer
and Clay recorded these for comparison while I read through the primary cover :
22° at 2500 RPM
28° at 3000
29° at 3500
31° at 4000
33° at 4500
36° at 5000
All of these are 3-5 degrees advanced, compared to the chart, and the 5K number spooked me out
I was almost at the end of my stator adjustment, but we moved it back (CCW) to the end of the slot, took 3 more reads (while the bike shook itself backwards on the center stand and we were obliged to shout at each other) and it was still about 1° high at 2500, 3000, and 4000. So I pulled the rotor and rolled it up about 3° clockwise, and next time Dave comes over, I expect to find the bike will be about 1 degree retarded, compared to the chart.

Observations and questions:
The tach on the bike is not calibrated well enough to catch these RPM readings. How can I improve this accuracy?
I had to butcher a plastic protractor to move the stator plate and rotor by 2 or 3 degrees at a time. Is there a good way to mark the housing?
MexicoMike thinks the curve I'm chasing is no good anyway. Does Boyer or Pazon offer anything better?
If the stock AAU is the gold standard, why are Boyer and Pazon curves so far away? In particular, why does Boyer have about 12 degrees of initial advance after decades of people telling them we are sick and tired of kickbacks?
The bike wants to stall out now more easily. Is it typical to have to reset carbs after re-setting timing?
And one more time: Anybody ever find the Boyer Mark IV advance curve?

The Mk3 Boyer is not a sophisticated bit of kit, but it was the best you could get 30 years ago. I still run the Mk3 Boyer that I fitted in 1983 and it is a first kick starter almost without fail.

The Mk3 makes its advance curve by electromagnetic induction in the pickup coils. As the magnets spin past them, a voltage is induced in the pickup coils and the black box " looks" at the voltage and when it reaches a certain level, the black box fires the coils and you get a spark. The faster the magnets wizz past the pickup coils, the higher the voltage induced and the sooner the spark is fired. That's your advance curve. Not rocket science but that's also why it keeps advancing past 3000 rpm.

I'm not sure how the Boyer micro digital system works but it might have a better advance curve.

I'm sure there are better systems on the market now but if you use a 30 year old design you can't expect perfection.

In answer to your question about idling, yes it's normal to have to adjust idle after you've reset the ignition timing.

Mr. Rick said:

The tach on the bike is not calibrated well enough to catch these RPM readings. How can I improve this accuracy?

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All you need to do is check/set it at full advance, so rev up until the ignition stops advancing.

Mr. Rick said:

MexicoMike thinks the curve I'm chasing is no good anyway. Does Boyer or Pazon off anything better?

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Yes, (digital) but they are more expensive. All the various analogue ignitions (Boyer, Pazon, RITA, SPARX, Wassell) seem to have similar advance curves (where known) and don't normally reach full advance until 4000-5000 RPM.

Mr. Rick said:

If the stock AAU is the gold standard,

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I'm not convinced it is the "Gold Standard" as it has no vacuum advance therefore is yet another compromise.

Mr. Rick said:

why are Boyer and Pazon curves so far away?

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But are they? Where can we see the dyno tests to prove it? If you wan't something better then why not buy one of the (much more expensive) digital systems?

Mr. Rick said:

In particular, why does Boyer have about 12 degrees of initial advance

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Where do you get 12 degrees initial advance from?
I believe the Boyer box advance is 12 camshaft degrees/24 crankshaft degrees (same as the AAU) which makes the initial advance about 7 degrees and the NSW page you linked quotes "6.8 degrees at 1000 RPM" so at kickstarting speed it would be even less.

Mr. Rick said:

after decades of people telling them we are sick and tired of kickbacks?

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So they introduced the MkIV box as kickbacks were generally caused by low voltage. I don't think they can be held responsible for those who got kickbacks because their ignitions had not been set correctly (36 degrees ) ?

Mr. Rick said:

The bike wants to stall out now more easily. Is it typical to have to reset carbs after re-setting timing?

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Yes.

There have been advance curve published here in the past that showed the curve for several of the popular e-ignition systems. I removed the Boyer that was on my '73 when I bought it in '06 and installed the OEM points specifically because of the better advance curve. I had no intention of switching back to e-ignition. However, when the Trispark came out I discovered that it had a curve very close to OEM, I decided to try it. That was back in '08 or thereabouts and its been on the bike ever since.

Frankly, on old-timey motors (before computer controls), as noted earlier, the best way to set advance was to just advance the ignition until pinging occurred than back it off a couple of degrees. On high performance tuning, you would put the engine on the dyno and increased advance until the power increase dropped and then put it back to whatever figure produced the max power and THAT would be the advance setting for that engine. It might be quite different between different examples of the exact same engine. I have seen over 6 degree differences for optimum timing in two essentially identical V8 engines.

If your commando does not ping under acceleration, do not worry that the timing is too advanced for the engine; it's not, WHATEVER the degree reading says.

Thanks, you guys, for yr comments and guidance, and especially to L.A.B., for the point-by-point critique.

I'll try to address the comments from Les in order:

If, as Pommie John points out, the Boyer keeps advancing, I will never get to the right place for calibration.

I wd settle for maxing out at 4K, but if the AAU maxes at 3K, I wonder why the makers think that 4K or 5K is better.

I don't think any of these systems have vacuum advance, not sure why this came up in a comparison context.

With reference to the different shaped curves and the 12 degrees of initial Boyer advance, I was using the chart seen here: www.accessnorton.com/NortonCommando/almost-stranded.24324/page-2
I'm pretty sure the Pazon is the Surefire model and the Boyer is the Mark III


My ideal system wd have wiring like the Pazon Altair, with a terminal block to eliminate all those foolish crimped connectors. If this bloody Boyer kicks me back one more time, I'm gonna pop for it. Anybody know a U.S. distributor?

Mr. Rick said:

If, as Pommie John points out, the Boyer keeps advancing, I will never get to the right place for calibration.

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It appears to stop advancing. If it concerns you that it continues to advance then check at higher RPMs.

Mr. Rick said:

I wd settle for maxing out at 4K, but if the AAU maxes at 3K, I wonder why the makers think that 4K or 5K is better.

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That would be a question for the ignition manufacturers.

Mr. Rick said:

I don't think any of these systems have vacuum advance, not sure why this came up in a comparison context.

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I was referring to the original points AAU. Vehicles (cars) often had/have a vacuum advance as well as a centrifugal advance as ideal ignition timing needs to adjust for load as well as RPM therefore any 'bobweight only' system is a compromise.

http://www.superchevy.com/how-to/ad...now-about-vacuum-advance-and-ignition-timing/

Mr. Rick said:

With reference to the different shaped curves and the 12 degrees of initial Boyer advance, I was using the chart seen here: www.accessnorton.com/NortonCommando/almost-stranded.24324/page-2

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The "Boyer (Comeau)" curve of that graph doesn't match dynodave's graph which I believe shows 0 'distributor' degrees at 200 'distributor' RPM (400 RPM) and 2 distributor degrees at 500 distributor RPM (so 4 degrees at 1000 RPM).

http://atlanticgreen.com/boyerexposed.htm

Following this thread...
incredibly funny reading indeed.
This, all followed 7 years of intense small block chevy mechanical distributor curve with vacuum advance work that I have not forgotten to this day and is the beginning basis of general ignition principals training.
MY initial work from 25 years ago when I was beginning norton ignition research (early 90's). Still mostly valid today.
Last weeks project...depot a norton trispark...completed... very interesting. thanks Wendy
Unfortunately I hate to type and won't do beltdriveman style online books.
Beautiful ride today on the MKIII with a beautiful LRLRLR boom boom boom boom, mile after mile

Well, if we have actually put a smile on Mr. Comeau's face, I think it's an accomplishment.

I had seen the "Boyer-Bransden" curve on the atlanticgreen site, and still don't know what to think of it.
If we can really extrapolate from that graph by multiplying each axis value by 2, to get the more usual "ignition degrees advance at engine RPM" graph, the Boyer curve wd read 14° at 3K and 19° at 5K . Clearly, my understanding has been surpassed. Again. Maybe it's an ancient Boyer, pre- Mark III?
Or maybe the initial advance needs to be added? If this is the case, and a Boyer is closer to 31 at 5K, the initial advance wd be 31 minus 19 = 12°, consistent with the graph above.

L.A.B. said:

It appears to stop advancing. If it concerns you that it continues to advance then check at higher RPMs.

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The Boyer curve seems to be still rising slightly at 5000 RPM according to the graphs I've seen.

PJ is correct:
All the capacitive charge ignitions never stop advancing/rising. The asymptote line is well above the max speed of any engine. In these cases the ignition does not have the same limitations as the physical limits of a mechanical device (engine).
Additionally...lacking a vacuum advance the ignition systems' technical design consideration is for "full throttle", therefore the most retarded curve is the most proper outcome. Having naively made assumptions about some of the early analog systems, I later learned (told by Ernie Brandson & his engineer) such as all MKIII boyers for all bikes were (theoretically) the same except the wire length and end connections. The second unfortunate truth is the lack of consistency of ignition curve is due to component tolerance variation. This is not an indictment of Boyer, just the truth. A sample of the curve variations from the "same" product is shown.
Additionally 2: I have long proclaimed and still stand by my statement that one ignition curve for all the engine applications is an unfortunate compromise. So here we are discussing these draw backs...

Mr. Rick said:

If we can really extrapolate from that graph by multiplying each axis value by 2, to get the more usual "ignition degrees advance at engine RPM" graph, the Boyer curve wd read 14° at 3K and 19° at 5K.

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The DD graph shows the apparent advance range.
As Dave says;

"To the uninitiated, the way to look at a distributor curve is to be, (1) very aware these are distributor degrees and distributor RPM, and that there is no such thing as initial advance until you install and set these components on an engine. Only at that point should you talk in terms of initial timing and engine degrees. The timing would then be 2 times distributor degrees plus initial advance)."

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Therefore, when set to a 'full advance' figure of 31 degrees (for Norton) according to the graph, the Boyer should retard 19 (crankshaft) degrees, full retard would then be 12 degrees!
However, according to the numbers on the NSW page, there's 24.7 degrees of advance/retard between 1000 (6.3 deg.) and 5000 RPM (31 deg.)!
Although the actual NSW advance/retard below 1000 is unknown, if it continued to reduce along the approximate line of the curve then I think it would probably be somewhere between 0 and 2 degrees at 'kickstart' RPM.

Mr. Rick said:

Is there any difference in the advance curves?
I think need a curve that starts with less advance than my current MK III during the kickstart routine. My ankle is killing me after a vicious kickback today, and I cannot afford to be crippled or afraid to start the machine, either.
I found advance curves for almost everything except the Mark IV, which does claim to have improved it's sensitivity to low voltage.

Click to expand...

My experience BoyerMK3

Bought 25 years ago MK3, there was only it on the market. 9 km and BOX H.S, guaranteed new box (A friend has of to make change 3 times, he dared to take up it since he is on a shelf ).
10 years later thread got away in the girdle from the trigger.
16 years later kickback: broken right foot.
8 months later New kickback: broken left foot.

All this with a battery with more than 12.5 volts and all the wires, reels, regulations makes by a friend motorcyclist electrician.

I am not unfortunately the only one has who it arrived in France and U.K

Since I am in contact breakers (9 years)

This ignition it is of the low-cost you get a good value for money no more rather less

Fortunately since a few years there are ignitions electronics much more reliable and more successful,like Trispark,Sachse etc....than this shit in the components of bottom of the range and in the very bad performances, disadvised moreover for the electric starter of the 850MK3

On the forums (UK, the USA, French) the problems with Boyers returns very regularly since many years ..............