Topic: Advancers CB500/550

[Deltarider]

Recently there has been a debate in the UK forum on the advancers used by Honda in the CB500/550s. A member had stated that different advancers have been used by Honda to provide different advance curves for different models 500/550, alas without presenting any proof. Unfortunately for him all Honda docs contradict him.
I've reminded the forum that Honda has used two different advancers: one by Hitachi and one by TEC (Toyo) and although the design was different, both were meant to provide the same advance curve. The parts lists are proof of that: you will find them both listed for all CB500/550 models. Since one member there insisted that the CB550Fs and the CB550K3 were totally different models that therefore needed other advance curves, I thought it wise to show that also the CB550F and the CB550K3 parts lists have both advancers listed. Alas the moderator had blocked the thread and as a consequence members are left with a falsehood.
IMO, the debate was much ado about nothing - I mean there's hardly an advance curve to speak of. I maintain however that I have never seen or heard of different advance curves, intended by Honda for the various CB500/550s. The parts lists are proof that Honda has used both indiscriminently. I thought it wise to bring the correct info. A good source is p.16 part #7 in: https://www.honda4fun.com/dwnload/Part-List/CB500/CB500-K3-CB550-K3-K4-Parts-List.pdf
This is not to start a debate about advance curves in general. The point is that members should realise they have a responsibility in providing correct information on matters especially where it concerns OEM parts. If one gives info that so far is unheard of, fine, but then it is not unusual to be asked to present proof or substantiation. This for the sanity of the forum. If such a modest request results in a rain of accusations, still without giving any proof and/or substantiation, it is IMO an unhealthy situation.

[PeWe]

It might be an advancer thread here somewhere?

If the old good "Thoughts of Hondaman" threads specify some advancers....

[bryanj]

It has been pointed out on the uk forum that Honda never stated an advance curve just max advance revs and that the dwell angle is only quoted in one part of the manual.
The big argument on there was Delta quoting anecdotes from a non mechanic as fact and getting upset when other members who have been making a living for decades as both Honda and multi franchise mechanics and have seen the Honda bulletins, service letters and memos that come through offical lines but of course dont have them to print out at the present so of course they cant be true

[Deltarider]

[...]
The big argument on there was Delta quoting anecdotes from a non mechanic

Where did I do that? Show us, please.

[...] !as fact and getting upset when other members who have been making a living for decades as both Honda and multi franchise mechanics and have seen the Honda bulletins, service letters and memos that come through offical lines but of course dont have them to print out at the present so of course they cant be true

No Bryan, that did not happen. In my last post I've even asked the moderator to compare the language I have used to the insulting language used by opponents.
And here you again with beating the drum of your year's experience. I'm sorry, Bryanj it has worn so thin by now that it is no longer valid in itself. IMO, you're still the best in the field, but this time you're wrong and the way you deal with it, well... it is not a pleasant sight. 
I have never heard of any intended difference in the advance curve of the Honda CB500/550s. Intended by Honda, that is. On the contrary: all info we find in the Shop Manual Honda CB500-550 is consistent: 5^o advance static and 30^o at full advance. The 30220-323-005 (Hitachi) as well as the 30220-323-154 (Toyo) advancer have been used by Honda indiscriminently over the various 500/550 models: the CB500s, the CB550Fs and the CB550Ks including the CB550K3s. There is NO service bulletin that suggests otherwise. Moreover: the proof is in the field. You'll find both advancers being used on a same model. And if I have seen that, you as a mechanic for so many years must have seen it also.
Never have I heard of a specific model advancer to be used on a particular CB500 or CB550 model. Me thinks that if that 'claim' has any truth, we should have seen the topic appear in this forum at least once in all these years the forum exists. Claimer took my request to come forward with proof and/or substantiation immediately as if I was doubting his expertise and he stressed - not for the first time - how many years he had worked as a mechanic. Such a defense can make me feel a bit uncomfortable. Can. Not always, but every now and then, I then doubt the validity of the claim. 
If I or any member can be asked to justify something, so can he. It's this principle the matter is all about. And if I can achieve we agree on this priciple, I have rendered this forum a great service. We can all accept arguments, we will NOT accept knockdown arguments.
IMO the thread was prematurely blocked and as a consequence members of that forum were left with a falsehood. I find this quite serious.
Now the fact that I have not heard of seen anything that can proof/substantiate his claim, is not so meaningful. It could be that all these years I have missed it. Could be, it is not likely, but it could. That's why I asked for proof and/or substantiation. Claimer has had ample opportunity for it. So far he didn't, but he still can. Should we have to apologise for even asking?

[Oddjob]

Quoting anecdotes from a non mechanic , that would be you Delta, you've never worked in the trade, have never been trained by any of the big manufacturers, have little to no practical knowledge, you just seem to study parts books and seem to think that makes you an expert. When you are challenged for some of your statements you immediately take offense, you go off topic and introduce other bikes into a conversation about one type of bike, you get nasty and say stuff like just go away and work on your own engine then post a video of it, you misquote stuff, you alter the posters comments and then quote them to make your argument better. As soon as anyone makes a counter claim you shout PROVE it, you then go on to say stuff that you can't prove, when challenged you start to throw your toys out of the pram.

As for you've never heard of any intended difference in the advance curve, I'm sure the letter from Honda was lost in the post, they'd never do anything without letting you know now would they. Both myself and Bryan have worked in the trade for many years, both have had Honda training, both worked for Honda main dealers, however at no time in the thread did we ever mention how many years that was, another invention by you. What might have been said was " In my many years in the trade" but that's not exactly beating you over the head with the experience gained during that time. I've lost count of the amount of Honda bulletins I've read, so many I can't remember most, was there ever one about the advance/retard unit on the 500/550? don't know TBH, just because I can't remember it doesn't mean there wasn't. You however assert there wasn't, prove it, show us the bulletin, hard to prove a negative isn't it yet that's what you constantly ask for.

As I've said before, AFAIK Honda didn't issue any details on the advance/retard units, they didn't issue a comparison between the 3 versions, not 2. Just because they didn't doesn't mean there wasn't, as you yourself pointed out the springs were different between the models, it's a well known mod to trim the springs to make the advance curve quicker, you can't interchange parts between the 2 models, why not, according to you they are identical.

As I've also said repeatedly, there is no dwell angle data issued by Honda for the 500K0,K1 or K2 or the 550F, (except as I've said repeatedly on the other thread, the data in the book for the Honda diagnostic machine, which contradicts your data) there is only dwell angle data for the 500K3 and 550K3, that's not the same engine, it has different carbs fitted, PD carbs, they use different exhausts, it was produced at a time when environmental issues were just starting to be addressed, it ran leaner than all the previous models, it's logical to assume it may have therefore needed a slight alteration in it's timing, that's when Honda started to list the dwell, why did they do that? if it was the same as the others why bother, Honda if nothing else were logical, the way their part number system works is pure logic.

I'm not going to start another debate on this forum, the thread was locked because of your attitude not other peoples, this will be my one and only post on the matter, I'm sure anyone reading between the lines can decide who's the idiot here.

[Deltarider]

Quoting anecdotes from a non mechanic , that would be you Delta, you've never worked in the trade, have never been trained by any of the big manufacturers, have little to no practical knowledge, you just seem to study parts books and seem to think that makes you an expert.

Wait a minute, Oddjob, now that the moderator of the UK site has blocked the thread, no one can see what the dispute was about and you can go on producing lies, just like you did in that thread. That is cheap. I can't remember I've quoted a mechanic in that particular thread. Please reproduce and I have a look at it. In general: if I do quote a mechanic it is, so anyone can value it for what it is worth. It is in line with that I always give my sources. Both you and Bryanj seem to interpret such a quote as 'evidence', which it is not and I find it quite telling and alarming you interpret it as such...

When you are challenged for some of your statements you immediately take offense, you go off topic and introduce other bikes into a conversation about one type of bike, you get nasty and say stuff like just go away and work on your own engine then post a video of it, you misquote stuff, you alter the posters comments and then quote them to make your argument better. As soon as anyone makes a counter claim you shout PROOF it, you then go on to say stuff that you can't prove, when challenged you start to throw your toys out of the pram.

Oddjob, I hope you are man enough to ask your moderator to - if necessary temporarily - to reopen that thread - not to continue it - but to make it possible for anyone to check the nasty accusations you made there and make again here. Will you, Oddjob? Please do. I can't wait.

As for you've never heard of any intended difference in the advance curve, I'm sure the letter from Honda was lost in the post, they'd never do anything without letting you know now would they. Both myself and Bryan have worked in the trade for many years, both have had Honda training, both worked for Honda main dealers, however at no time in the thread did we ever mention how many years that was, another invention by you. What might have been said was " In my many years in the trade" but that's not exactly beating you over the head with the experience gained during that time. I've lost count of the amount of Honda bulletins I've read, so many I can't remember most, was there ever one about the advance/retard unit on the 500/550? don't know TBH, just because I can't remember it doesn't mean there wasn't. You however assert there wasn't, prove it, show us the bulletin, hard to prove a negative isn't it yet that's what you constantly ask for.

Well, we don't need a bulletin, just show us proof there were different advancer curves. I have never seen it in practice and it has never been a topic, so you can't blame me for being curious. All I know, nobody ever brought it up before and all Honda docs seem to contradict you. Again, can't blame me for being curious. Have you had already a look at p.16 in the CB550K3 parts list? You, that were so sure that K3 model needed a special curve.

As I've said before, AFAIK Honda didn't issue any details on the advance/retard units, they didn't issue a comparison between the 3 versions, not 2. Just because they didn't doesn't mean there wasn't, as you yourself pointed out the springs were different between the models, it's a well known mod to trim the springs to make the advance curve quicker, you can't interchange parts between the 2 models, why not, according to you they are identical.

I'm afraid you still don't get it. Why were both listed then in all these parts lists without specifying to which engine serialnumbers it applied? How was a mechanic to decide which to mount, if they were different in their curve as you and Bryan stubbornly maintain without even a hint to proof. Why creating this crazy myth that nobody has heard before? If I hadn't asked for proof, I'm sure someone else would have.

As I've also said repeatedly, there is no dwell angle data issued by Honda for the 500K0,K1 or K2 or the 550F, (except as I've said repeatedly on the other thread, the data in the book for the Honda diagnostic machine, which contradicts your data) there is only dwell angle data for the 500K3 and 550K3, that's not the same engine, it has different carbs fitted, PD carbs, they use different exhausts, it was produced at a time when environmental issues were just starting to be addressed, it ran leaner than all the previous models, it's logical to assume it may have therefore needed a slight alteration in it's timing, that's when Honda started to list the dwell, why did they do that? if it was the same as the others why bother, Honda if nothing else were logical, the way their part number system works is pure logic.

Thank you for repeating the nonsense you wrote before in the UK site. Saves me work.
Here's what will make you happy. The following can be checked by anyone, including you. Just work on enough CB500s, 550Fs, 550Ks including the K3 and you will see in reality the advancers provide the same curve. I've seen it and so can you. So you don't have to believe horrible me. You can check it for yourself. I'd say: grab the occasion!

I'm not going to start another debate on this forum, the thread was locked because of your attitude not other peoples, this will be my one and only post on the matter, I'm sure anyone reading between the lines can decide who's the idiot here.

The more reason for you to ask your moderator to reopen the thread, so all can see the language used by me and by you. In my last post I've friendly asked the moderator to compare my language to the language of others including you. And also in that last post I gave a link with the evidence that settled the dispute once for all, but maybe your moderater judged that evidence not particularly welcome. Telling, isn't it.
I really hope your moderator has the courage to reopen the thread, not to continue it, but so that anyone can read how my request for proof or substantiation was answered.
All in all this is good example and a warning, how members who take it lightly with the truth, will be met. Don't be tempted to spread nonsense, or face the consequences, no matter your curriculum vitae. Ipse dixit.

[calj737]

Let me see if I understand THIS thread clearly: there was a dispute on the UK forum, and that thread has been locked. So you, Delta, in an undying effort to prove your mini science, have brought it over to this forum? Despite what trained, certified professionals tell you, you choose to argue with them based upon word of mouth from “friends”.

Ok, got it. 

[Tracksnblades1]

Quoting anecdotes from a non mechanic , that would be you Delta, you've never worked in the trade, have never been trained by any of the big manufacturers, have little to no practical knowledge, you just seem to study parts books and seem to think that makes you an expert. When you are challenged for some of your statements you immediately take offense, you go off topic and introduce other bikes into a conversation about one type of bike, you get nasty and say stuff like just go away and work on your own engine then post a video of it, you misquote stuff, you alter the posters comments and then quote them to make your argument better. As soon as anyone makes a counter claim you shout PROVE it, you then go on to say stuff that you can't prove, when challenged you start to throw your toys out of the pram.

As for you've never heard of any intended difference in the advance curve, I'm sure the letter from Honda was lost in the post, they'd never do anything without letting you know now would they. Both myself and Bryan have worked in the trade for many years, both have had Honda training, both worked for Honda main dealers, however at no time in the thread did we ever mention how many years that was, another invention by you. What might have been said was " In my many years in the trade" but that's not exactly beating you over the head with the experience gained during that time. I've lost count of the amount of Honda bulletins I've read, so many I can't remember most, was there ever one about the advance/retard unit on the 500/550? don't know TBH, just because I can't remember it doesn't mean there wasn't. You however assert there wasn't, prove it, show us the bulletin, hard to prove a negative isn't it yet that's what you constantly ask for.

As I've said before, AFAIK Honda didn't issue any details on the advance/retard units, they didn't issue a comparison between the 3 versions, not 2. Just because they didn't doesn't mean there wasn't, as you yourself pointed out the springs were different between the models, it's a well known mod to trim the springs to make the advance curve quicker, you can't interchange parts between the 2 models, why not, according to you they are identical.

As I've also said repeatedly, there is no dwell angle data issued by Honda for the 500K0,K1 or K2 or the 550F, (except as I've said repeatedly on the other thread, the data in the book for the Honda diagnostic machine, which contradicts your data) there is only dwell angle data for the 500K3 and 550K3, that's not the same engine, it has different carbs fitted, PD carbs, they use different exhausts, it was produced at a time when environmental issues were just starting to be addressed, it ran leaner than all the previous models, it's logical to assume it may have therefore needed a slight alteration in it's timing, that's when Honda started to list the dwell, why did they do that? if it was the same as the others why bother, Honda if nothing else were logical, the way their part number system works is pure logic.

I'm not going to start another debate on this forum, the thread was locked because of your attitude not other peoples, this will be my one and only post on the matter, I'm sure anyone reading between the lines can decide who's the idiot here.

Very informative….

Just curious what does Honda do when their professional support team can’t fix the problem…

Here in the USA I heard GM Ford JohnDeere Caterpillar has a process….just wondering how Honda took care of the bad apples…?

Thanks in advance…

[grcamna2]

I would be interested to know if there is any difference in advance curves between the various CB500/550 advance mechanisms. 
When we clip-off a half or a Full coil from one or both of the advance mechs,I imagine that changes the advance curve slightly?  I ask as one of the uninformed members and for the purpose of learning:nolo contendere 

[Tracksnblades1]

I would be interested to know if there is any difference in advance curves between the various CB500/550 advance mechanisms. 
When we clip-off a half or a Full coil from one or both of the advance mechs,I imagine that changes the advance curve slightly?  I ask as one of the uninformed members and for the purpose of learning:nolo contendere 

I read that too. But I thought when the spring’s coil was snipped off it delayed the timing advance curve. Or at least tightened the advancer spring back up where Honda wanted them. I’ve read posts that the shortening (tightening) the springs eliminated the spark timing scattering about at an idle too.

Perhaps the 500/550 advancers work differently than the 750…?

[bryanj]

I can say from experience that the travelling techs for Honda in uk always sorted any problem, first recorse was phone help the a rep

[seanbarney41]

So easy to settle this argument...get out the the degree wheels and start measuring the advancers

[PeWe]

Can the advance springs really provide a certain curve that will last?
If advancer is controlled by vacuum another repetative thing.

Or by software CPU box calculated advance like Dyna 2000 or so.
The CB500 racers use Dyna 2000 too, right?

I have seen as noted earlier, springs to make sure that the advance does not happen too early.
A hotter cam shaft like not too early advance too.
Idle more stable when springs will  keep advance stable. Slightly off carbs must cause the soft springs to let advance to jump even worse.

The earlier posts about CB5x0 is max advance around 3000rpm, right?
I know that CB750 like full advance from 2600-2700 as my bikes

I would like an advance curve as my K6 with cut springs, but it will advance a little more AFTER 7000rpm

That's a curve!

I retarded it a little when cruising in low (legal) speeds (ca 3000rpm) felt "hard". Compression might have helped that. I imagine it runs softer there after a little retard,  plate outer edge moved 1mm clockwise. Might have lost a pony or 2 at the top.

AD125-1 (Hitachi) with cut springs, verified on dyno.



The race forum has posts about electronic ignition where advance can get good curves.

I fully understand people using a device like this. With an advance curve
Keep advance from happen too early with a little extra later on.
Throttle sensor next step.

Like this:
https://www.ignitech.cz/en/vyrobky/tcip/tcip.htm

Sh!t!!!
I have to verify the ignition on dyno coming season.
As now and advance back as before, 1mm counterclockwards.
I have had thoughts about it since  carbs got better jetted.

Always things to adjust and test.
A programmable advancer, no compromises.

Let spring happen very soon!!

[Deltarider]

If anyone, no matter his background, says something new/unusual, something that has never come up before, that person can expect, when it contradicts what another knows, from experience and  Honda docs, to be asked for proof and/or substantiation. I did just that. Immediately the reaction was like if that person felt cornered and then - you can wait for it - the usual summing up of: 'professional training', so many years in workshops, short lines with Honda etc, etc, came up again. In other words: who are you to dare to ask me that? But... I didn't ask for a curriculum vitae, I asked for proof that could explain his deviation from what we have known for decades.
The data on the ignition including the advancers which Honda used in the CB500/550s has been out for decades. Some assume that if there's a difference in design between the different suppliers Honda had, there will be a difference in the advance curve as a consequence. This is not the case and it has been proven. Better even: anyone can check it for him self!
The first manual I got in 1981, was the Clymer. On page IX, you will find the dwell angle specified. That angle is the same for all CB500/550s and even all CB350/400Fs, notwithstanding the advancers used by Honda originated from different suppliers. Years later I have found this confirmed in the official Honda docs. Actually I have been pleased with that info, because I could now remove the dust from my old analogue dwell/tachmeter I had purchased in the 70s at a high price. Bloody expensive, because made in Switzerland and in continental Europe we all know that as far as precision instruments, the Swiss make the best, especially if such instrument has a dial.
In the automotive industry it's not uncommon that manufacturers have more than one supplier for certain parts. I remember my model Peugeot which had no less than three suppliers for the alternateur, mounted on the very same model!: Ducellier, Paris-Rhône and the ones assembled in Belgium had Bosch. All three had exactly the same specifications.
The same goes for the advancers Honda has used indiscriminently even on the same model. Parts Lists of all CB500/550s (except for the very, very first about the CB500), had both advancers listed. For a mechanic it was safe to fit either the Toyo or the Hitachi one, just like he can fit either NGK sparkplugs or the equivalent made by Denso.
Now to the data about the ignition. You can check the Shop Manual Honda CB500-550, including the addenda for the CB550, CB550F and even the CB550K3 and let me know if you can detect any deviation from the 5^o static and 30^o at full advance. There isn't ofcourse, because the same parts have been used, even on the CB550K3 and F2. And - no surprise - also the parts lists of the latter two models, list both the Toyo and Hitachi advancers. I cannot see how you could arrive at a different advance curve and experience has confirmed this.
As expected opponents have failed to falsify these data we all know since decades and can see confirmed whenever we want in everyday practice. Instead of such, I was supposed to have shown more respect for someone who... 'professional training', so many years in workshops, short lines with Honda etc, etc.
I've put it to them that this is the internet where we can't see each others blue eyes and where anyone can just present himself the way he likes.
@Calj

Let me see if I understand THIS thread clearly: there was a dispute on the UK forum, and that thread has been locked. So you, Delta, in an undying effort to prove your mini science, have brought it over to this forum? Despite what trained, certified professionals tell you, you choose to argue with them based upon word of mouth from “friends”. Ok, got it. 

Thank you for your reaction, Cal; I knew I could - as always - rely on you. Your reaction is particularly valuable because it clearly demonstrates the attitude that brings a hazard. Nobody is above the law and the rules in a forum, apply for anyone IMO, the more as on the internet we are invisble and don't know eachother. We are not in church where you are expected to kneel for something you can't see. Nor are we in the army where the superior officere knows best - even when he doesn't
I don't know how old you are, but let me assure you that the military is on a constant look out for exactly your mentality. Now, if that isn't good news...   

[PeWe]

I think Hondaman has written about the different advancers with max advance, weights, how to adjust max arms can move etc.
For both CB750 and 500
http://forums.sohc4.net/index.php/topic,7401.msg67251.html#msg67251

[MauiK3]

Weights and springs are pretty simple stuff, in this day of high speed electronics I can't visualize how the weights and springs are much different than the old rotating ball governors on old steam equipment where gravity is the spring. I don't think it's really a curve as much as it is a straight line until the limit or as the old saying went "balls out"

[Deltarider]

The advancer used on the CB500/550 could not have been simpler, the more when one remembers the advancers we used to have in cars, which worked partly with centrifugal force and partly with vacuum (better: underpressure). Maybe some of you have at least once overlooked a vacuum tube that had come loose, like I have.
Advancer is actually a misleading term. Retarder would have been better, because - believe it or not - the thing is only there to facilitate easier starting. If we wouldn't need a retarded timing for starting, we could run our bikes always at an ideal advanced timing, 30^o BTDC. Have a look at the advancer below. The yellow mark indicates 5^o BTDC. Easy starting is then guaranteed. But my bike starts just as easy at 8^o BTDC. So no worry if it isn't spot on 5^o BTDC. Concentrate on a correct timing at full advance of around 30^o instead, say from 2800 RPM on. Full advance is indicated by the two marks, one blue, one green. They are 3^o apart and I'll come to that next.
I've always used genuine Honda parts and on my bike, they are by TEC (TOYO), but things work just the same with Hitachi parts.
Out of curiosity I once experimented with setting things exactly spot on and then vary the dwell.
With timing static set at exactly 5^o and a dwell of exactly 49^o (= 0,3mm gap), full advance would be at the first full advance (blue in the pic) mark, 28,5^o. When I changed the dwell to 46^o (= 0,4mm gap) full advance would be at the second full advance (green in the pic) mark, 31,5^o. I am sorry to say I have not completed the experiment by repeating this for 2+3. I was quite impressed by the accuracy of Honda parts and even more when I choose the middle: a dwell of 47,5^o (= 0,35mm gap) which not only resulted in a full advance right between the two full advance marks 30^o but also, as a bonus, having all components in the middle of their adjustment range. When I helped a friend who had a Daiichi plate and breakers, I did not arrive at having components in the middle of their adjustment range, when I choose the middle. I'm not saying Daiichi parts are therefore bad, they're are just different. In the past I have suggested that Daiichi in the US must be Chinese imitations of the Daiichi sets we have in Europe which were made in Japan. I know quite some riders here, that have satisfactorily results with them. As said: the US market is another story.
Now I always have my ignition 2-3^o more advanced which results in a better throttle respons (driveability) but that's up to anyone's liking and it could also be fuel related.
Now to those little springs in the advancer. I have two CB500/550 advancers and both still have their original springs. I have no complaints and in spite of their long service, there is no need to cut any coils. Why would I do that, if RPM drops immediately to a steady idle the very moment I close the throttle? I have NO experience with CB750 advancer springs and it could be that on those models cutting a coil can be a remedy. I have no experience with CB750s. Mine (CB500) work fine. If for some reason a CB500/550 owner experiences a somewhat fluttering idle and he suspects sloppy springs, I'd advice him not to cut a coil but tweak the ultimate coil around the mount a bit. A friend who owns a CB500 had success with that. Simple and no costs involved.
When you want to order new springs, realise that the Hitachi and Toyo springs differed in length. (pic courtesy Marco). Some very, very experienced British mechanics, well trained and having worked many years in workshops (I mention this, before we forget ) concluded that thus the TOYO and the Hitachi advancers must have a different advance curve. That conclusion is wrong. Both Hitachi and TOYO, although different in design, will provide the same advance curve.
I always advice to begin simple with a feeler gauge when setting the breakerpoints gap. If you have a dwellmeter, I'd use it. Then you can set the breakerpoints dynamically and also check the dwell remains constant and does not wander when RPM changes. Checking the timing is best done using a strobe, but, I would not attempt to adjust the timing dynamically. Plates will move about and it can become a frustrating experience. Better is: adjust timing, then check at full advance. Then stop the engine and make the needed adjustment, start engine again and check again at full advance. You may have to stop the engine again for a further adjustment. This procedure works best. Just accept the timing @ idle it will result in.
I have stressed many times that (re)setting the gaps comes first, because it is there, where the timing begins to deviate from the ideal. As a matter of fact: usually just resetting the gaps (dwell) is the only thing you have to do, to arrive at the correct timing again. Makes sense, the plates are well fastened and don't wander. At least not that I seen.
Last remark: genuine breakerpoints maybe expensive, but they live very, very long indeed. In the 110.000km I have rode my bike, I cannot remember that I have renewed them more than just once. Wear by pitting occurs most at idle.

[Tracksnblades1]

For those interested. The advancer used on the CB500/550 could not have been simpler, the more when one remembers the advancers we used to have in cars, which worked partly with centrifugal force and partly with vacuum (better: underpressure). Maybe some of you have at least once overlooked a vacuum tube that had come loose, like I have.
First this, 'Advancer' is actually a misleading term. Retarder would have been better, because - believe it or not - the thing is only there to facilitate easier starting. If we wouldn't need a reduced timing for starting, we could run our bikes at always the ideal advanced timing, 30^o BTDC. Have a look at the advancer below. The yellow mark indicates 5^o BTDC. Easy starting guaranteed. But my bike starts just as easy at 8^o BTDC. So you don't need to aim for a spot on 5^o BTDC. Concentrate on a correct timing at full advance of 30^o BTDC say from 2800 RPM on. Full advance is indicated by the two marks, one green, one blue. They are 3^o apart and I'll come to that.
I've always used genuine Honda parts and on my bike, they are by TEC (toyo), but things work just the same with Hitachi parts.
Long time ago, I experimented by setting things exactly spot on and then varied the dwell.
With timing static set at exactly 5^o and a dwell of exactly 49^o (= 0,3mm gap) full advance would be at the first full advance mark, 28,5^o. When I changed the dwell to 46^o (= 0,4mm gap) full advance would be at the second full advance mark, 31,5^o. I was even more impressed by the accuracy of Honda parts when I choose the middle: a dwell of 47,5^o (= 0,35mm gap) which resulted in full advance right in between the two full advance marks 30^o. I then had all components in the middle of their adjustment range. When I helped a friend who had a Daiichi plate, I did not have components in the middle of their adjustment range. I'm not saying Daiichi is therefore bad, it's different. In the past I have suggested that Daiichi in the US must be Chinese imitations of the Daiichi we have in Europe that were made in Japan. I know quite some riders here that have satisfactorily results with them. As said, the US market is another story.

Good info Delta….

That’s why you alway set the dwell first…back in the mechanical point gap days…😁

Yes, changes in point dwell changes the timing because it’s changing the point gap. The distance from the points block to the the points cam…thank god dwell is electronic now…

As for the vacuum advance canisters on old cars. Remember Chevrolet alone had vacuum advances from as little as 12* to as much as 24*. As well as different pull in and drop out vacuum ratings depending on compression,cams, vehicle weight, transmissions, rearend ratios, etc.. For instance a 69 302 special high performance/high compression with a solid lift Duntov cam with two 780 holleys, headers supplied by Chevrolet in the trunk, idling at 9” vacuum required a very different vacuum advance than say a grocery getter with a 454, 7.8:1 compression and a two barrel..

Quick  throttle openings during high rpm part throttle cruise (static+centrifugal+vacuum, total timing) could result in detonation when using the wrong vacuum advance with the wrong compression ratio, octane, or any of the above mentioned ….Ford 460s had the highest combined timing over 60* BTDC if I remember correctly…

 thank god the 302/z28s had four speeds transmissions so we don’t have to mention power valve vacuum activation and drop out vacuum ratings in combination with vacuum advances…Power valves could get interesting with long duration cams and automatic transmission and their varying neutral vs drive idle rpm and vacuums…🤪

[Tracksnblades1]

Weights and springs are pretty simple stuff, in this day of high speed electronics I can't visualize how the weights and springs are much different than the old rotating ball governors on old steam equipment where gravity is the spring. I don't think it's really a curve as much as it is a straight line until the limit or as the old saying went "balls out"

Some more of that steam engine language

“Balls to the wall” or “Balls against the Walls”

[HondaMan]

I know that CB750 like full advance from 2600-2700 as my bikes

I would like an advance curve as my K6 with cut springs, but it will advance a little more AFTER 7000rpm

There is a way to do this: both the mini-car racers I knew in the 1970s who used CB750 engines (sans trannies, cut those right off, ran an external oil pump off the #1 side of the camshaft) and, of all companies, Ford, did exactly this with their engines. The Ford method is much simpler than the racer's versions were.

In my 1967 Ford there were 2 different springs on the spark advancer: one was weaker and the other was stronger, but it also had a long loop in the end of it and was mounted to the opposite post from the weaker spring. So, the weaker spring ran from 950-ish RPM all the way to the end of the longer loop inside the stronger spring, but the stronger one added a slowdown to the curve's angle, and was weaker than the primary spring. This change was: from 950 RPM to about 2000-ish RPM the big 390 CID "H" engine had linear advance of a quick rate for lively in-town throttle response, and when the advance weights had opened up to engage the loop in the 2nd spring, the advance continued, but at a slower rate. At 6500 RPM the advancer weights hit the stops (I modified the springs to get full advance by 4800 RPM after the USA stuck us with the infamous 55 MPH speed limit nationally). However, in top gear the car was going about 125 MPH at 4100 RPM and still accelerating: the speedometer stopped the indicator at the point with a little pin. The car kept on speeding up: I really don't know what its top end speed was. In 2nd gear (it had 3 speeds) it could run up to 120 MPH, passing any slower vehicles with great ease.

I miss that car...