Boyer Bransden ignition timing setting

TXA Phoenix

TX650A Phoenix
Messages
49
Reaction score
0
Points
6
Location
Phoenix, Arizona
I've installed a Boyer Bransden Micro Power Ignition on my 1974 TX650A.
It was easy to follow the instructions and align the mark on the crank rotor to the unlabelled full advance mark on the stator and then align and set the white dots on the magnetic rotor to the holes on the stator plate. This allowed for easy starting. The Boyer instructions then call to
"strobe time on the front or full advance mark by reving up the engine and watching the timing move up to the mark. Adjust by moving the stator plate."
I'm having a problem with these instructions because I obviously think that it is necessary for the advance timing marks to come into alignment at a precise RPM. Which should be what full advance timing is when using the centrifugal advance which was designed with the engine. I've read two sources for this value. One was 3000 RPM and the other was 3200 RPM. Does anyone know the true and correct value? I imagine it could be found by strobing on the centrifugal advance weights and using a precise digital tachometer and noting at what RPM they move completely out.
Since the Boyer ignition digital unit is suppose to be programmed for optimal spark advance adjusting at units of 50 RPM from idle to full advance isn't it obviously necessary to set it precisely?
I've contacted Boyer by email and they only offer senseless answers of maybe this RPM and maybe that RPM. They won't answer at what RPM does the digital unit provide full advance. That's what I need.
I'd like to save myself some money and set it correctly myself if I had the correct values rather than taking it to the bike shop and having it dyno tuned. Does anyone have any opinions or information on this situation? I've been reading about the Boyer Bransden posts on this forum but none seem to be exactly related to this one.
 
It would be comforting if there was one true and correct answer to things in life wouldn't it? I rarely find that to be the case though. Even in a super modern engine control system full of feedback sensors and computers there is no one "correct" timing. The ideal time depends on a long list of things that are continually changing. They have tables of predicted values that *should* be right in theory if all the sensors measuring throttle position, air temperature, engine temperature, mass air flow, rpm, and engine load are perfectly accurate and the vehicle is still exactly like the new 100% factory example the computer expects to find itself in, BUT even with all that worked out it's still unpredictable so they throw in a knock sensor and dial back the timing from the calculated "correct" value as needed. No two cycles of the engine produce the exact same result, it chaotic and turbulent in there.

One thing is for sure, you wouldn't want to base your answer on watching the mechanical weights. There's a reason they ditched it. If you look at all the threads here about that pesky mechanical advance unit I get the impression it was too inconsistent for you to get a number that's anything more than what this bike you're measuring did. This year. Before the springs sagged out a little more and the weights and slots wore a little looser. And who knows if that was ideal in the first place or just what was reasonably decent at a price they could afford in a package with few parts?

I'd try both settings you're considering and ride it. If you can't tell which one is better by doing that then there's not enough difference to worry about, and you'd know it's definitely not worth worrying about those 50rpm divisions that have 1/4 of the effect that was already too small to notice.
 
Some of the old boyers you had to set them at over 4000 revs, the system for a Moto Guzzi was supposed to be set at 5000 rpm, I normally rev it until it stops moving then you know it's fully advanced.
 
Your reply doesn't make a lot of sense to me and you use some guess work. I still think the Boyer instructions should provide an RPM at which full advance comes into play for their system and should be based on emperical evidence rather than setting full advance at a "rev range" which is somewhat arbitrary. That basically is what my post is about.
I never had any problems with my mechanical advance and points/breaker set up. I got good gas mileage and could take the bike to 110 MPH. When I rebuilt the bike I wanted an easy set and forget system which used a higher spark because the 1974 650 has a weak spark and is noted as such in the Clymer Publications manual.
I'm trying to work with the Boyer Bransden system but they don't seem to offer qualified answers. Rather than trying various RPM settings for full advance I'd rather try a whole new system and I am thinking of replacing it with a Pamco system.
 
Your reply doesn't make a lot of sense to me and you use some guess work. I still think the Boyer instructions should provide an RPM at which full advance comes into play for their system and should be based on emperical evidence rather than setting full advance at a "rev range" which is somewhat arbitrary. That basically is what my post is about.
I never had any problems with my mechanical advance and points/breaker set up. I got good gas mileage and could take the bike to 110 MPH. When I rebuilt the bike I wanted an easy set and forget system which used a higher spark because the 1974 650 has a weak spark and is noted as such in the Clymer Publications manual.
I'm trying to work with the Boyer Bransden system but they don't seem to offer qualified answers. Rather than trying various RPM settings for full advance I'd rather try a whole new system and I am thinking of replacing it with a Pamco system.
 
Last edited:
When I was running the Boyer setup, I would always set it at 3,500RPMS. Not sure what the advised RPM is, but that worked out perfectly for me. I know thats not official help or anything, just personal experience.
 
TXA, it's a mistake to think that the Boyer electronic advance should put the timing at 40*BTDC (the full advance mark) at the same rpm as the much cruder mechanical timing unit. If you try to do that you'll be running farther advanced than 40*at higher revs, and your pistons will not thank you. To time the Boyer, set the timing plate so that 40* is the maximum advance you hit when you turn up the revs, no matter where that occurs--crank 'er up until the mark stops moving.

If you want finer tuning, take a seriously fast ride of a few miles, chop the ignition, and read the clean burn line on the spark plug center wire. If the clean burn area is too wide, retard the spark a couple of degrees; read Gordon Jennings' article on plug reading at www.strappe.com for the procedure. I usually wind up at around 38* BTDC.
 
I'm trying to help but hey, go ahead and throw out your Boyer and put the shaky weights and springs back on if that's what lets you relax. The "empirical evidence" you think you need would come from a cylinder pressure sensor, not watching a primitive mechanical solution to the problem. You want the peak cylinder pressure to occur approx 15 degrees after TDC at all rpms, temps, air fuel ratios, loads, and throttle positions. Whatever the system used to get there, that's the goal. It should be obvious the mechanical one isn't even close to perfectly achieving that and you apparently were satisfied with it, so why is "close enough" okay for the the mechanical one but unacceptable for the Boyer? At least the Boyer will stay how you stay how you set it and should have a lot less scatter.

All I'm trying to say is every bike, environment, and rider is its own situation so you should tune it. Thinking one magic number someone gives you online is perfect and another only 200rpm different is crap isn't the right mindset to approach it. Even in much more sophisticated ignition systems timing is always an approximation and a compromise, and that's a fact not conjecture. Look it up if you're interested in this stuff. You're the only one in a position to find a good compromise for your setup, location, and riding style.
 
Last edited:
Over-complicating this dood....

Set motor to full advance mark.

Align red dot on the magnetic trigger with the hole on the stator plate marked "TIMING"

Kick it a few times to try and fire it off. I have found that the best way to do this is to keep making incremental adjustments until the bike starts easy and idles fine. Trying to adjust the stator plate while it's running is difficult, most times you'll adjust too far out of range and the bike will die.

Once it's idling nicely, take the strobe, point it at your timing marks, hit the throttle, and watch the advance rise, then stop when it hits full advance, somewhere between 3000-4K. The RPM isn't what's terribly important, it's making sure the strobe and the timing marks are aligning to full advance.

This is really helpful:

http://www.650motorcycles.com/BoyerMicroPower.html

99% of the dudes replacing their new boyers with pamcos didn't install or set them up correctly.
 
TXA, it's a mistake to think that the Boyer electronic advance should put the timing at 40*BTDC (the full advance mark) at the same rpm as the much cruder mechanical timing unit. If you try to do that you'll be running farther advanced than 40*at higher revs, and your pistons will not thank you. To time the Boyer, set the timing plate so that 40* is the maximum advance you hit when you turn up the revs, no matter where that occurs--crank 'er up until the mark stops moving.

If you want finer tuning, take a seriously fast ride of a few miles, chop the ignition, and read the clean burn line on the spark plug center wire. If the clean burn area is too wide, retard the spark a couple of degrees; read Gordon Jennings' article on plug reading at www.strappe.com for the procedure. I usually wind up at around 38* BTDC.

Your answer is a contradiction in itself. Either by mechanical means or electronic means full advance should be the same.
 
When I was running the Boyer setup, I would always set it at 3,500RPMS. Not sure what the advised RPM is, but that worked out perfectly for me. I know thats not official help or anything, just personal experience.

Thanks for your answer based on personal experience. It provides a value for setting the timing rather than just somewhere in the rev range.
 
I'm trying to help but hey, go ahead and throw out your Boyer and put the shaky weights and springs back on if that's what lets you relax. The "empirical evidence" you think you need would come from a cylinder pressure sensor, not watching a primitive mechanical solution to the problem. You want the peak cylinder pressure to occur approx 15 degrees after TDC at all rpms, temps, air fuel ratios, loads, and throttle positions. Whatever the system used to get there, that's the goal. It should be obvious the mechanical one isn't even close to perfectly achieving that and you apparently were satisfied with it, so why is "close enough" okay for the the mechanical one but unacceptable for the Boyer? At least the Boyer will stay how you stay how you set it and should have a lot less scatter.

All I'm trying to say is every bike, environment, and rider is its own situation so you should tune it. Thinking one magic number someone gives you online is perfect and another only 200rpm different is crap isn't the right mindset to approach it. Even in much more sophisticated ignition systems timing is always an approximation and a compromise, and that's a fact not conjecture. Look it up if you're interested in this stuff. You're the only one in a position to find a good compromise for your setup, location, and riding style.

When I used the word emperical I meant that a dynamometer would be used to set ignition timing so that best horsepower at the rear wheel would be achieved for each RPM range. And that's what I would assume the advantage would be of using an electronic ignition using a microprocessor is that the processor would be programmed to do that. And it would only be able to do that when set exactly to the means in which it was programmed.
I really think there is a better and objective means in setting the timing of this system rather than setting the full advance mark somewhere in the revved position as the Boyer instructions state. It just serves as a switch to full advace somewhere in that revved RPM range. That's why it runs poorly out of full advance and I shouldn't have to play hit and miss with the adjustments to find which is right. At least the system using the "shakey weights" had an objective and quantitative means to set them properly.
It seems I'm getting responses from people who have stock in Boyer Bransden. I'm also wondering if the digital unit for the XS is a unit for a british twin with just an XS label slapped on it. It would seem to explain the elusiveness of getting a good answer from them.
 
I will never understand why people who clearly already know it all come to these forums and ask for advice just so they can disagree with it.

Good luck with your dyno tune the difference between full advance at 3000 vs 3200 plan. Should be good for at least 0.2 horsepower and hey if that isn't worth spending hundreds of dollars dyno tuning to pick up then you're just not serious about building the best 43 horsepower 500 pound bike money can buy right?
 
I will never understand why people who clearly already know it all come to these forums and ask for advice just so they can disagree with it.

Good luck with your dyno tune the difference between full advance at 3000 vs 3200 plan. Should be good for at least 0.2 horsepower and hey if that isn't worth spending hundreds of dollars dyno tuning to pick up then you're just not serious about building the best 43 horsepower 500 pound bike money can buy right?

I don't know it all. I'm still ready to accept an answer based on objective evidence. BTW it's 53 BHP@7000RPM and weighs in at 439 pounds.
 
Grizdl1 is right on the money. This is exactly what I would do.

TXA, it's a mistake to think that the Boyer electronic advance should put the timing at 40*BTDC (the full advance mark) at the same rpm as the much cruder mechanical timing unit. If you try to do that you'll be running farther advanced than 40*at higher revs, and your pistons will not thank you. To time the Boyer, set the timing plate so that 40* is the maximum advance you hit when you turn up the revs, no matter where that occurs--crank 'er up until the mark stops moving.

If you want finer tuning, take a seriously fast ride of a few miles, chop the ignition, and read the clean burn line on the spark plug center wire. If the clean burn area is too wide, retard the spark a couple of degrees; read Gordon Jennings' article on plug reading at www.strappe.com for the procedure. I usually wind up at around 38* BTDC.

You are focusing too much on the engine rpm. What's important as Grizdl1 explained is the degrees BTDC at full advance.
The specific engine rpm is not important as long as its high enough that the ignition module is putting out spark at the full advance setting.

IF this were a picture of the XS 650 Boyer advance curve you can set your timing for full advance anywhere from 2400 - 6000 rpm. It doesn't matter because as of 2400 rpm and above the advance will not change anymore.
advance curve.jpg


If I remember right stock setting is 40' degrees BTDC

And of course you want to do this with a timing light.

Chris
 
What's not objective about setting it to reach full advance at 3000 and 3200 and actually seeing if it makes any difference? That sounds a heck of a lot more objective than sitting around speculating about which one is "perfect". Pick up a wrench, get out there and try things, and take some responsibility for the performance of your bike man.

BTW that's just a crankshaft on a test stand. The MOTORCYCLE puts out 43. And unless you're gonna run it without oil or gas somehow, no, it's not 439... but keep up the know it all corrections cause it's really making people want to help you.
 
Correct me if you know otherwise.
On the Boyer Bransden Micro Power Ignition you CANNOT adjust at what rpm full advance occurs. The ignition module controls that. You CAN adjust at what degrees BTDC full advance occurs at.
 
Exactly, 650rmw. Pay attention, TXA and GreasyC, because I'm not going to try to explain this again. The OEM mechanical advance depends on spring tension on the bobweights to control at what rpm full advance occurs; it's not a very precise system. The Boyer Micro Power unit advances the spark in a continuous curve controlled by semiconductors. If you set the Boyer timing plate to hit full advance at rpm lower than the revs at which the Boyer box stops advancing the spark, the box will overadvance the spark when you exceed that rpm. I hope you don't need an explanation of just why that can cause very serious problems.

But you guys think you're smarter than Boyer, so you must be a helluva lot smarter than I am. Have fun entertaining yourself with the dyno; the guys operating it will be plenty entertained when you tell 'em what you want to do.
 
Hey now! Don't lump me into this craziness. He's the one trying to outsmart boyer. I'm the guy telling him NOT to go down a crazy dyno testing road. I don't know how I could be more clear about that. I'm saying over and over again there IS NO PERFECT TIMING so there's no point asking for magic numbers. If he really did this and tweaked the timing at every RPM for max power in a controlled dyno room his bike would self destruct as soon as he took it outside into the real world where temperature and fuel quality change every day. The boyer isn't any more magically "right" for every bike, gas, throttle position and environment than the xs box or mechanical thing is. They're all just compromises and HOPEFULLY ones made towards the side of safety because running a slow old bike on the ragged edge of detonation in a quest to get 46 horses instead of 43 is ridiculous.

Does it make you feel better if I add a link to the instructions instead of telling him to stop worrying about making it perfect? Then here you go but I assume he already has them: http://www.boyerbransden.com/pdf/KIT00103__BOX00010_.pdf
 
Back
Top