Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: paulbaker1954 on August 05, 2019, 11:45:31 AM
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OK now at wits end completely. New head gasket fitted (OEM), carbs fully overhauled and check of all pilot circuits etc and still running like a dog.
Checked for air leaks around carb rubbers etc
Symptoms are it starts up fine and sounds fine but as engine gets warm I get a afterfire in exhausts 1 and 2 and it will just not pull at all.
Am beginning to wonder if I have an ignition problem. The bike was fitted with a full Boyer kit including micro coils 18 months ago.
Anyway here is my question.
As I understand it the BOyer system fires all four cylinders so if this is correct I should be able to swap plug leads 1 and 2 over to 3 and 4 and vice versa. If I then get the problem on cylinders 3 and 4 instead of 1 and 2 it points to either a plug cap or lead or other ignition issue.
A further question is if I can just swap over the yellow and blue wires on the Boyer stator plate and will this have the same effect as swapping over the plug leads
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I see that as the same as you for both questions, it will swap different sections though.
The odd thing is from their strategy it should be cylinders 1 and 2 fired from different high tension supplies, so why would they both give problems unless there's something in their "secret" crossover electronics that is causing a related fault to travel down both routes. Just thinking out loud really there.
I would try both of those diagnosis changes separately to see what effect they generate, then discuss findings.
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Good point there
the Boyer system is 2 mini coils each with 2 HT outlets so am guessing each coil feeds 2 cylinders rather than there being 4 coils if you see what i mean ie the sam as the Honda original concept
I have also emailed Boyer to ask what other tests they can recommend
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🤔Honda SOHC/4's only have 2 coils, with 2 HT leads coming out of each. I'm I not understanding the question Paul 🙄🙄🙄🙄🙄
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Yes as above, the Honda system has one coil supplying cylinders 2 and 3 switched by one set of points, and the other set doing 1 and 4. It's easy to spot faults as they run completely independently of each other apart from voltage supply from ignition switch, making fault finding very logical if you work down each discreet line to plugs.
What the later Boyer claims to do is crossover even those two discreet systems so each pickup fires both coils with their internal switching :o so difficult to see what is going on.
So plugs one and two would normally have seperate supply integrity, but now are linked in some way if that makes sense. So a little confusion in trying to diagnose what's happening.
See if you get anything from swap testing that's going to shed any light on it.
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It could be something really simple. Years ago my speedway bike would start easily and then die on the start line as it was revved. I thought it was the magneto and swapped it out but still the same. It turned out to be the spark plug breaking down under compression but only when it got hot. The plug was a NGK and something I didn't expect given their reputation.
Are all your spark plugs new Paul? It might be worth swapping them over to see it the missfire follows them around?
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Agree Dave, trouble is I forget who's had new plugs or not when these symptoms get more reluctant to be resolved ;D
If they are not verified it would be good to do so.
What I don't understand is the connection between 1 and 2 as they should be discreet for HT response even if they were triggered by common switching.
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the one common item to 1 and 2 is fuel supply,
I run a Boyer,and you can put any plug lead on any plug,and it still runs .
mine had a similar issue about 5 yrs ago,,I got new plug caps and plugs,
not sure what cured it,but,touch wood,its OK now
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Yes the Boyer system does not help when it comes to diagnosis, I have emailed Boyer with the symptoms to ask what tests can be done so I will also see what they come back with
What I don't know is how the Boyer Micro coils work as they are digital and current driven as opposed to voltage driven but I do know that the system fires all cylinders at once as opposed to the original Honda set up that fires 1 and 3 and 2 and 4 together (wasted spark).
Looking at the picture of the coil pack it is clearly different to a conventional coil in some way and is sold as a "dual output" device. I am therefore assuming that if there is an issue with it it will be see on the the 2 cylinders it feeds assuming 1 coil feeds 2 cylinders
The wiring diagram Boyer supply shows the coil pack feeding 1 and 4 and the other feeding 2 and 3 but until I can get to the bike I cant remember how I wired the HT leads in. Not sure why they show the wiring like this if all cylinders are fired at the same time anyway.
The other "unknown" is what purpose the yellow and blue feed wires from the stator plate do in the Boyer control box it could be that there is a wiring fault between the stator plate and the Boyer unit.
Anyway seems like I am still on a learning and testing curve but I will post more as things develop hoping that it may be of use to others down the line diagnosing Boyer systems
One useful thing is Boyer will do a full test on any system for £17 and if there is a warranty fault the fee is not charged anyway.
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I didn't consider that you may have them arranged like that, 1 and 2 supplied from one coil. In that case if it's installed that way, then it could be something on that one coil causing you problems.
That'll teach me to assume it's going to be arranged as per Honda layout if that's the case.
I have distant memories of being schooled in the statement of "assumption is the parent of most f*ck ups" ;D
Be interesting to see what you've got on there.
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I didn't consider that you may have them arranged like that, 1 and 2 supplied from one coil. In that case if it's installed that way, then it could be something on that one coil causing you problems.
That'll teach me to assume it's going to be arranged as per Honda layout if that's the case.
I have distant memories of being schooled in the statement of "assumption is the parent of most f*ck ups" ;D
Be interesting to see what you've got on there.
Actually to be pedantic its a Bruce Willis quote from the Die Hard films as in "assumption is the mother of all f*** ups"
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Paul,
interesting info about Boyer micro digital ign, they declare power consumption less than stock, I just wonder how this can be if all coils fires at the same time (2x more sparks)?
I was thinking in the last days to buy, but will rather wait a bit - curious to see what will be result of your investigation
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Paul,
interesting info about Boyer micro digital ign, they declare power consumption less than stock, I just wonder how this can be if all coils fires at the same time (2x more sparks)?
I was thinking in the last days to buy, but will rather wait a bit - curious to see what will be result of your investigation
Could be a while - I have very limited Garage time over next few weeks :( :( :(
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I didn't consider that you may have them arranged like that, 1 and 2 supplied from one coil. In that case if it's installed that way, then it could be something on that one coil causing you problems.
That'll teach me to assume it's going to be arranged as per Honda layout if that's the case.
I have distant memories of being schooled in the statement of "assumption is the parent of most f*ck ups" ;D
Be interesting to see what you've got on there.
Actually to be pedantic its a Bruce Willis quote from the Die Hard films as in "assumption is the mother of all f*** ups"
We were told that in the late 1970s as apprentice by somebody who tutored us but worked in air accident investigation at Farnborough, so I'll claim the technical high ground on that one with your kind permission Paul ;D
Now I've just got to have a word with Mr Willis regarding copyright ;D ;D
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Can you refit the original points etc, bit of a bugger I know but would confirm where the fault lies.
I could but the old well knackered coils went in the bin a long time ago !!
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I don't think coils differ much from one to another, just the specification matched to however they are being switched making them tailored to the Boyer full system. That is as opposed to switching original coils with lesser spec Boyer triggering.
The digital refers to their non mechanical control of ignition advance as far as I can see from their published data.
If you take the obvious example of Honda advance / retard mechanism as first form of ignition timing control, then the type you get on cdi units (explained by Ash in his cdi thread) as both being mechanical / physical.
Digital control in the Boyer appears to consist (my own overview) of zero offset on at what we'd consider "maximum advance" then digital retardation of anything below that in rpm terms. So looking essentially back to front from how we'd normally interpret it.
Because you can't advance from a trigger point that has not occurred at the crank you can't design the system from base setting and go forward as you are waiting for trigger signal to initiate the whole process.
Taking that signal and comparing it to a internally stored LUT ( look up table, or standard matrix graph in simple terms) with axis of revs versus time delay, it will give a read out of ultimately the time it has to add to any command of switching the coil as you move downward from the setup revs. So building a retard curve that the unit acts on dependent on engine revs pulse from crankshaft trigger unit. Et voila, "digital" ignition curve. Still has to be converted to analogue though via power handling transistors to switch the coils on and off.
Add in a floor setting of say 750 rpm, below which it starts to reduce any time delay, and you get an anti stall system of sorts as cutting the switching delay below that advances the ignition and tries to accelerate the motor. As revs come back up toward 1000rpm the time delay increases back to maximum to bring timing back to normal tickover setting. Very simple and no setup required.
Having the timing setup at the maximum advance point also avoids the possibility of any inaccuracies causing too much advance as it's just not possible to trigger it earlier, so you get an assured maximum advance accurately working direct off the crank with no mechanical or otherwise interference.
The bit I don't get is why they link the two set of coil firing. It doesn't hurt but I can't rationalise the reason. You definitely need two crank triggers to go with the two pisons up and two down mechanical design, but see no combustion advantage in linking them.
It would provide redundancy if one crank trigger failed, I guess. But is that the reason?
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can I make a comment,
the coils should connect to plugs 1 and 4 ,and 2 and 3
its to do with piston position
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Ok all I am now beginning to get both more confused and maybe a bit clearer.
I went back and checked last night and my Boyer system is connected as per their instruction i.e. 1 coil to 1 and 4 and the other coil to 2 and 3.
So this may have buggered up my theory on my problem as the afterfire is on 1 and 2 so now thinking it may not be Boyer related at all ::) ::) ::)
I have been thinking bacjkto what changed since it was last running well and apart from head gasket and carb cleaning the one other thing i remembered was i added some new short lengths of nitrile fuel tubing from the petcock and joined these to the main carb feeds with 90 deg elbows (This was to make it easier to get the tank on and off).
These were a bit of a squeeze in and I had to shufty stuff around a bit to stop the feed pipes from the petcock kinking as the nitrile tubing I got has a much thinner wall then the original Honda tube feeds.
So now for my next theory ------ I think what is happening is that as the bike warms up and things expand/move around that the feed to 1 and 2 is getting kinked and starving 1 and 2 of fuel to an extent. This would account for the afterfire on 1 and 2 only from a much weaker mixture as well as the hard pick up off the line when I guess fuel demand is quite high.
As a bit of further evidence I remembered that when I was syncing the carbs with an aux tank that all seemed to be running well until the bike warmed up and then I heard the afterfire. I noticed that the carb sync connection tube to No 1 had come loos so I guess this introduced an air leak again causing a very weak mixture and hence afterfire on Cyl 1.
All this has to be confirmed with some more testing when I have some time but I wanted to know if my logic above makes sense.
As to the Boyer system it is still interesting to learn more about the system for future diagnosis etc.
Below is the reply I got from Boyer for the record that confirms you need to connect 1 coil to 1 and 4 and 1 to 3 and 3 NOT any to any as I thought.
Thank you for your enquiry, check you have a coil firing 1 and 4 cylinders and a coil firing 2 and 3 cylinder. They do fire together but should be on compressed cylinders alternatively.
You can swop the coils over or leads, you may have a faulty coil.
Check the plug caps for resistance no more than 5000 ohms.
The clips into the HT side of the coils should be soldered, no spark gaps.
Theory is yet to be tested as I am awaiting some much thicker wall fuel hose
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Logically you'd need to look at what changed to makes sure it's not caught you out in compromised fuel supply, sounds a sensible plan to eliminate it.
"Usually" the characteristics of reduced supply are with compromised higher demand.
The float chambers are obviously filled to allow a small reservoir for each set of carb jets to work with. If the supply is slow or restricted then at tickover you'd not generally see it, but at larger constant throttle opening the demand outstrips the inflow causing cylinders to cut out at higher speeds. Slow down and the demand drops below supply volume then cylinders chime back in. So in effect the opposite of your symptoms.
So, puzzling, but you've got to check everything in something like this to make sure something is not missed.
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Agree but I guess it depends on how restricted the supply is.
If supply is really bad then even at tickover you will see fuel starvation. I also have bad running at higher revs by the way.
The afterfire occurs intermittently every minute or so at tickover so I think what is happening is that the fuel input rate vs output is behaving somehow non-linearly for some reason. Start up is fine then runs until float level is low enough to trigger a weak mixture and the afterfire and then some kind of fluid dynamics behaviour is happening causing the cyclical nature of the fault.
I could test this theory by connecting my home made manometer to the drain screw and observe what happens to the float level. That said I don't know what the level should be doing under normal tickover, I guess it should be constant around the normal higher level (ie around 2-3 mm below bowl/carb join line).
Anyway this is all interesting stuff and purely theory at this stage. We will see when I do some more experimentation !!!
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If your really stuck Paul I could lend you a set of coils, a points plate complete with everything and an advance retard mechanism for a few days. Just took them off my bike last week. They were working great when I stored it 30 years ago, should still work now I reckon.
Thanks Ken offer much appreciated :)
Am now leaning a bit more to this being a fuelling problem so want to isolate this first. I will shout out if I need help
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It's a pain for you trying to sort it, but it does make us think about how some parts work.
It's rare to find any failure posts about Boyer as they do seem reliable. Just that if you don't know what's going on inside them it's more of a problem in situations like this to try and eliminate causes.
Also I've rarely seen a confirmed as failed (original equipment) coil, cars or bikes. Often suspected and chucked out during substituted diagnosis, they seem genuinely robust to me.
As far as I view it, float level should remain more or less constant whatever demand is placed on it from running engine, else jetting would just not be reliable enough to run accurately. Think you need about 10 times cross section of delivery flow compared to main jet size to make sure the supply doesn't impinge on engine demand.
Your test will show the levels at least for you to assess if it's too variable. If it can just about fill up float chambers when not running, it has the potential to outstrip the supply with it going. Any significant drop during use would potentially give fuel starvation.
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Well I think I have finally got to the bottom of thing.
Not a fuel starvation issues as when I hooked up the aux tank with no kinks etc then no change
Then After swapping coils, hot leads, plug caps etc all over still no change
Finally I happened to be tugging at the carb bank and hey presto ran smooth and no after firing
Juggling the carbs up and down def causes the issue to come and go
So final conclusion air leaks at the inlet rubbers
New (OEM) ones ordered up (ha ha note Graham if you are reading this) so hopeful this will be the end of it 🤞🤞🤞🤞🤞
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Make sure you order new clips as well, apparently the new OEM ones are slightly thinner rubber, and the original clips don't quite do up tight enough!
Sent from my POT-LX1 using Tapatalk
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Make sure you order new clips as well, apparently the new OEM ones are slightly thinner rubber, and the original clips don't quite do up tight enough!
Sent from my POT-LX1 using Tapatalk
Really??? I just put new OEM ones and i did not observe it. Old clips fits well.
but did not measure old and new rubber, will check next time
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Make sure you order new clips as well, apparently the new OEM ones are slightly thinner rubber, and the original clips don't quite do up tight enough!
Sent from my POT-LX1 using Tapatalk
I have only found this on the 750's as, it is a superseded number ;) ;)
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I am now wondering if your originals were aftermarket ones fitted in the States..... before DK bought it and imported it here. They did seem rather soft and definitely not consistent with Honda ones used for a few thousand miles ... ones from the States are usually prone to hardening much more than UK bikes, probably down to hotter climate in a lot of the States DK tend to buy from. I am pretty sure yours were slightly softer than my NOS ones ..plus it's not just the hardness properties of the rubber it is also it's resistance to 'compression set'.
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I am now wondering if your originals were aftermarket ones fitted in the States..... before DK bought it and imported it here. They did seem rather soft and definitely not consistent with Honda ones used for a few thousand miles ... ones from the States are usually prone to hardening much more than UK bikes, probably down to hotter climate in a lot of the States DK tend to buy from. I am pretty sure yours were slightly softer than my NOS ones ..plus it's not just the hardness properties of the rubber it is also it's resistance to 'compression set'.
Ash that would make sense if course as i have no idea of previous history of course
Its interesting that the seal kind of suddenly failed as the carbs have been off and on lots of times.
Maybe just this last fit was the straw that broke the camel’s back so to speak
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Hopefully you've got to the bottom of it with these.
At least the idle circuits will be clean and ready to run when you get the parts on it ;D
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Bugger still no further forward, fitted the new OEM head/carb rubbers over the week-end and still bad.
I have
- Swapped the plug caps over - no change
- Swapped the plugs around
- Swapped the actual coils over - no change
- Then swapped the coil leads over
I have now noticed something else going on, bike starts and runs fine and I have my carb balancer rigged up and can see there are no "jumps" in vacuum which I think I would see if there is an air leak.
Idling is good and then as the bike warms up the afterfire starts to happen and is intermittent. Will run for 30s and then bang, then run for say 1 min and then bang bang again.
So something is happening that I think is some function of temperature. Also on a couple of occasions I have had it completely cut out and have no spark at all as the bike gets hot. Allow the bike to cool down for 15 mins or so and fires up perfect again.
I have also bypassed the loom by running a separate pair of wires from the Boyer stator plate to the Boyer box in case there is some slight break or resistance in the blue and yellow wires that feed the Boyer box.
I am racking my brains and nearly going insane now trying to figure this one out now and have decided to send the whole Boyer kit back for testing to at least eliminate some temp related issue with the Boye box or the pickup coil on the Boyer stator plate.
- Anyone any more bright ideas to try
- Anyone near Warrington prepared to lend me a hand if the Boyer kit checks out OK, I am getting to the point when maybe 2 heads are better than 1 here
- Alternatively anyone know a suitable mechanic I could pay around Warrington, bike is running so temperamental I daren't try and ride it anywhere I think
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Running out of logical things to check on this.
To the slightly illogical, try moving the timing first advance and then retard about 2 to 3 degrees and run it at both setting to see if you get an improvement or worsening.
Have you considered re-checking the camshaft timing too?
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The only input I can put into this is that as all 4 spark plugs fire at the same time, is it possible that one cylinder is over fuelling and has an exhaust valve open as the spark occurs???
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Running out of logical things to check on this.
To the slightly illogical, try moving the timing first advance and then retard about 2 to 3 degrees and run it at both setting to see if you get an improvement or worsening.
Have you considered re-checking the camshaft timing too?
Camshaft timing is OK, I treble checked it when I put the head gasket on and am 100% confident its OK
Think I will just see what the Boyer testing comes up with and then go from there.
The only consistent thing I can identify is the few times that it has just cut out and died completely. When this happens there is then no spark at all and then fire up again fine once I leaveit for 15 mins or so.
I hate chasing down sporadic issues like this and this one is really beginni to do my head in >:( >:( >:(
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The only input I can put into this is that as all 4 spark plugs fire at the same time, is it possible that one cylinder is over fuelling and has an exhaust valve open as the spark occurs???
Interesting theory, but the issue is on 1 AND 2. Any ideas on how I could check for this though?
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It sounds very similar to the symptoms I had on a Trident 900 when the ignition pickup coil started failing. It ran perfectly until hot, then backfired and cut out. Leave for a few minutes and would start and run for a short time.
I replaced the pickup coil and it was sorted. Maybe you have a rare Boyer failure? It'll be interesting to see what the testing finds.
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It sounds very similar to the symptoms I had on a Trident 900 when the ignition pickup coil started failing. It ran perfectly until hot, then backfired and cut out. Leave for a few minutes and would start and run for a short time.
I replaced the pickup coil and it was sorted. Maybe you have a rare Boyer failure? It'll be interesting to see what the testing finds.
That is really interesting, I too was wondering if it could be the pick up coil issue. Boyer charge £17 for a full system test and if its a fault and its warranty they dont charge so I figure worth getting it checked anyway
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Unsure of wiring diagrams for Boyer, but usually a coil is earthed via the points on conventional systems.
With electronic "pickup " they don't have that facility on most type systems, just a trigger pulse that comes from exiting the receptor or chopping a light beam.
That must mean the coils are earthed via the power transistors in the electronic control pack, in effect switching the earth supply up and down at this point remotely from "points / trigger" assembly.
What is that earth route? And can you supplement it with something like a jump lead to engine cases to check it's ability to support switching competently.
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And after that, the positive supply to the system to verify that too.
Both of these can checked by taking a run of independent wire straight to the battery + or - terminals to bypass anything else within the bike's own systems, switches etc.
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[attach=1]
Earth route is via the black lead from Boyer box that is connected straight to Battery Neg post. At least as I understand it !! No issues with this and checked.
I have bypassed also the loom with my temp cable from the stator pick up points direct to the Boyer control box ie the yellow and blue wires that normally go to the coils
Only think I haven't done yet is take a temp direct feed from the battery Pos to the BOyer box to eliminate any issues with loom/kill switch wiring.
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That wiring diagram has two black wires indicated to the box, is that true? Or have they just missed thet"white" description going to the ignition supply connection?
Not possible to switch those two is it?
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That wiring diagram has two black wires indicated to the box, is that true? Or have they just missed thet"white" description going to the ignition supply connection?
Not possible to switch those two is it?
Not sure I follow you. Yes there are 2 black wires (bad practice IMO). On the K0 there is a black and white wire that terminates in a double connector near the coils. This is the +ve feed for the 2 coil leads. On my Boyer I use the double +ve connector for the black supply feed and the feed to the + side of the coil. All is deffo wired as it should be.
As I said one last test would be to run a single +ve feed straight from battery connected to the coil and box. Then there is no Honda loom in the equation anywhere
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My grammar there I think in trying to clarify, I was looking at it and wondering if it said what I was thinking ;D
So, if the two black wires from Boyer box have the same terminals? Could they be inadvertently connected the "wrong" way round? Ie earth to pos and corresponding opposite, making the Boyer box be in effect wired opposite polarity.
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My grammar there I think in trying to clarify, I was looking at it and wondering if it said what I was thinking ;D
So, if the two black wires from Boyer box have the same terminals? Could they be inadvertently connected the "wrong" way round? Ie earth to pos and corresponding opposite, making the Boyer box be in effect wired opposite polarity.
No they are def connected correctly. Am now erring towards some electronic or wiring issue but what I cant get my head round is why the after fire only occurs on 1 and 2. Now down to either a wonky +ve feed to the Boyer box and coils OR a fault in the Boyer stuff (Sure it's not the coils as I swapped these over). Going to put this post on hold for a couple of weeks till I get the test results back from Boyer
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I fitted Boyer to mine and it ran bad I took it to D&M engineering it turn out after hours of fault finding the box was faulty they put a Dave silver unit on all problems solved. Turns out that I wasn’t the first one with this issue with the Boyer system.
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have you got the old coils<
maybe they could be breaking down when they get hot
or,can you use a multi meter to check resistance etc
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http://www.sohc.co.uk/index.php/topic,8209.30.html
See reply #41
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http://www.sohc.co.uk/index.php/topic,8209.30.html
See reply #41
Thanks but all is wired as per Boyer instructions. Complete Boyer kit including box, stator plate, rotor and micro coils going back today for testing.
See what they say and move on from there
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I encountered a similar problem on a friend's CB550 back in 1988. In the end we binned the electronic ignition and went back to points.
Recently, I was on the verge of converting mine to Boyer, but I think this thread has put me off the idea :)
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I encountered a similar problem on a friend's CB550 back in 1988. In the end we binned the electronic ignition and went back to points.
Recently, I was on the verge of converting mine to Boyer, but I think this thread has put me off the idea :)
Lets not jump the gun it may not be the Boyer set up but I am running out of options >:( >:( >:(
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I encountered a similar problem on a friend's CB550 back in 1988. In the end we binned the electronic ignition and went back to points.
Recently, I was on the verge of converting mine to Boyer, but I think this thread has put me off the idea :)
I’m running Boyer with their micro coils, first class operation. Nice bit of kit. Would highly recommend it.
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I encountered a similar problem on a friend's CB550 back in 1988. In the end we binned the electronic ignition and went back to points.
Recently, I was on the verge of converting mine to Boyer, but I think this thread has put me off the idea :)
I’m running Boyer with their micro coils, first class operation. Nice bit of kit. Would highly recommend it.
As you say, £17 to eliminate it or confirm it’s the culprit, will be worth it.
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Ah well wouldn't you know it, Boyer stuff was on soak test for a day and all checked out fine, stator plate, coils and ign module so am still chasing this really frustrating problem down.
Here is what happens in a bit more detail.
Bike starts, runs fine and idles lovely but as things warm up the afterfire starts occuring. It is sporadic and not at all regular and occurs only on 1 and 2.
Here are my thoughts
1) I don't think this is carb related as idling etc is prefect until things warm up. I am going to hook up a manometer to the float drain to watch what happens to fuel level though.
2) I am running now with the Boyer stuff connected direct to battery and with a new 2 core cable from stator plate to Boyer. In other words nothing Boyer related is going through the loom
3) It seems Boyer box can suffer from RF and/or stray AC leaking in to the wiring so I have tested Rectifier Diodes and all good so doubt any AC leakage but I am going to check with an AC ammeter to double check.
4) I am also going to try running with the Boyer stuff powered from a completely separate spare battery
5) I have checked the plug caps (NGK) and 3 are at 5K Ohms and 1 at 4.3K Ohms (new cap ordered in case that 1 cap is the issue.
6) have bought a new Elextrec Rectifier/Reg unit but not fitted yet as the original Diodes check out OK, will fit if ther is AC leakage or no charge coming through from exisiting rectifier
I have to say this is THE MOST frustrating problem I have ever had >:( >:( >:(
Have I missed anything obvious I should be dooing testing wise/checking to track this issue down finally
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have you checked the valves i.e. compression test and valve clearance.. sorry if you already have, I didn't read back through the whole thread. I had a misfire on a 550 many years ago which I initially thought to be ignition or carburation related... but after much frustration I ended up having the valves re-lapped which solved the misfire and totally transformed the motor..
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have you checked the valves i.e. compression test and valve clearance.. sorry if you already have, I didn't read back through the whole thread. I had a misfire on a 550 many years ago which I initially thought to be ignition or carburation related... but after much frustration I ended up having the valves re-lapped which solved the misfire and totally transformed the motor..
Compression good on all 4 cylinders, actually valves were all re-lapped in only 1K miles ago. Valve clearances all good and valve timing double checked.
One thing I haven't done is check compression again once warmed up which is probably a good idea
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I can't remember if you said you had the barrels off this engine, in other words have you seen all of the piston rings?
Frustrating as you say as you've verified most things.
Offer of std ignition to check setup by eliminating current system would be useful.
How have the carbs been synchronised?
Which number plugs are you using?
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Yes barrels been off very recently and rings all good in fact they are new pistons and rings only 2k mies ago.
Carbs synced with vacuum balancer
Will check plugs but was running fine on these plugs before
I should add this all started after a head gasket change and cleaning and adjusting of carbs
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Try synching the carb's with Bryan method of mechanical setup and run it like that. Don't put the guages on it at all.
Then setup the idle air screws as per Honda manual routine. It's very specific as to how it should be carried out for initial setup after carb rebuild.
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Just an additional thought, all the syncing blank screws are in place aren't they? Non have fallen out?
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I had one engine do similar- noticed after thrashing its useless carcass 20 miles each way to and from work that one of the valve stems became discoloured from heat. It only did this after a frustrating long lot of use - not investigated it further just dropped the motor and swapped it for another. It's an outside possibility but I suspect mine was down to a sticking valve. It came into play with a hot engine, fine in the garage, naff on the roads.
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Try synching the carb's with Bryan method of mechanical setup and run it like that. Don't put the guages on it at all.
Then setup the idle air screws as per Honda manual routine. It's very specific as to how it should be carried out for initial setup after carb rebuild.
Where can we find that?
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Oh... and how about the exhaust gaskets? Are they well fitted and seal well?
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Try synching the carb's with Bryan method of mechanical setup and run it like that. Don't put the guages on it at all.
Then setup the idle air screws as per Honda manual routine. It's very specific as to how it should be carried out for initial setup after carb rebuild.
Where can we find that?
I'll get a photo and post it of the page, but wont get to manual until the morning. That's of the idle setting method, but it shoukd be in one of Ash's manual files too.
Bryan method here http://www.sohc.co.uk/index.php/topic,17769.0.html
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Just an additional thought, all the syncing blank screws are in place aren't they? Non have fallen out?
Or missing the sealing washer
Actually I have bike set up for testing with carb balancer connected. I nterestingly if I pull off one of the vac hoses from the brass connecting pipes there seems to be no change
Is this any clue
Will try and post a vid on u tube over next few days so folks can hear what is happening
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Just one cylinder that does that? Or any one you try? Revs should rise if you pull one of the tubes, check the brass tubes to see if one of them is obstructed, I'd start with that one you've just pulled off and compare it to another.
What I'm angling at is that the guages are causing you to put mechanical error onto carb setup. Hence request to set them as Bryn does to take the guages etc out of the equation.
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I'll get a photo and post it of the page, but wont get to manual until the morning. That's of the idle setting method, but it shoukd be in one of Ash's manual files too.
Bryan method here http://www.sohc.co.uk/index.php/topic,17769.0.html
Thanks and looking forward to it. As far as bench syncing, I have my own method that worked well at three different occasions. As a matter of fact, I haven't touched my gauges for decades. BTW, it is particular the mixture setting by the airscrews for the oldstyle Keihins that I'm interested in.
I nterestingly if I pull off one of the vac hoses from the brass connecting pipes there seems to be no change
Paul, that indicates something is not right, it should make a difference. To me it seems, there's some airleak already/overlean situation where pulling of the pipe does not makes much difference anymore.
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This thread may help you Delta.....this is relating to Keihins which have air screws (where the screw is at the air box, or back side of the carb, not fuel screws which are at the engine side, or front of carbs) So this covers most, if not all of the carbs fitted to our bikes. I bench sync all carbs with Bryans method and then adjust air screws as per that thread and the carbs are spot on. No need to vacuum them at all.
http://www.sohc.co.uk/index.php/topic,19585.0.html
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Thanks Julie, I'll study it with interest. I have two socalled air/fuel testers (oldstyle) lying around that both suffer from bad connectors in the leads but that for the rest seem to work OK. I have to figure out how I can improve these connectors to be able to do some experiments (my bike has 4-4). But that may take a wile due to... laziness.
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[attachimg=1]
Above is photo of 750 K0 official workshop manual covering this method.
See what you think as I'm looking at it with a perspective of other systems and picking through how I recognise various bits.
It is essentially repeated in following Honda manuals I have for later bikes, it doesn't change apart from the direction of adjustment screw as it moves to engine side of carbs. It's very concise and does pick up on the elements that shoukd be optimised.
Remember though that the vac guage method on here is for the first iteration of this bike with 4 throttle cables and no synchronised lifting bar as later carb sets have. It's the idle trim after getting slides into equal positions that is common across successive carbs.
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Fingers crossed may have it cracked yet to road test but seems to be running well
Combination of a number of things
Fuel level too high on 1 and 2 (odd as I bench tested 2 times before refitting carbs)
Small air leaks at inlet rubbers (still there a bit - need some better clamps see separate post)
Dodgy rectifier connection (May have been causing voltage spike to Boyer system)
One plug cap was only 4.2k ohms which may have also been affecting Boyer kit
As I say yet to road test but running much much better and misfire all but gone 😀😀😀
Thanks to all who have been contributing to this post that’s what this forum is for!!!!
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Paul, wish you found root cause and issue is fixed!
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Paul, wish you found root cause and issue is fixed!
Sadly road test not good, now down to air leaks at inlet rubbers I think. The new clips I bought from DSS just don’t clamp up properly. Ordered some thin jubilee clips from INOX fasteners to hopefully fix.
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Paul, wish you found root cause and issue is fixed!
Sadly road test not good, now down to air leaks at inlet rubbers I think. The new clips I bought from DSS just don’t clamp up properly. Ordered some thin jubilee clips from INOX fasteners to hopefully fix.
Did mention issues with the clamps a few weeks back!
Sent from my POT-LX1 using Tapatalk
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Paul, wish you found root cause and issue is fixed!
Sadly road test not good, now down to air leaks at inlet rubbers I think. The new clips I bought from DSS just don’t clamp up properly. Ordered some thin jubilee clips from INOX fasteners to hopefully fix.
Did mention issues with the clamps a few weeks back!
Sent from my POT-LX1 using Tapatalk
Indeed you did but Graham commented this was only an issue with the 750 ones.
What really threw me is that I checked for air leaks with carb cleaner and couldn't find anything with engine running at idle in garage.
I then spotted that if I rock the whole carb bank up and down a bit then air then gets in and idle goes all over the place and misfire happens signifying air leakage.
I don't know but I guess also that when on the road and trying to pull away there is a a greater vacuum under load just making it all worse.
I checked one of the clips on a rubber and found that I can still rotate the clip just by hand when it is fully pulled up.
I think the these clips are DSS part number 9501844250 and they claim they are OEM that supersede the original part number. That said I am not 100% sure they are stamped with a number 44 on them. I think I will email DSS and get them to check their stock to see if they also have this 44 stamped on them.
I will report success or not when my new jubilee clips arrive this week.
I really hope this is the end of the road for what has been a very trying issue to get to the bottom of
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Fingers crossed its finally got to the root of it. Thankfully for the rest of us theres a ton of good checks on this thread which will be a good revisig point when one of us is having similar issues. Hope changing those clips finally sorts it.
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Well new inlet rubber clamps fitted and still no luck
I have finally given in and going to take bike to a good local guy who does classic bike race prep etc and knows fours and is highly recommended
He and I think this is an idle circuit problem on carbs 1 and 2 but I am now valuing a 2nd opinion and am running out of time and patience
I made a video of the afterfire noise and would appreciate any opinions
Vid is here and the afterfire is on 1 and 2 equally
https://youtu.be/TlWc7hyagG0 (https://youtu.be/TlWc7hyagG0)
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Oh er, what a strange noise. Sounds like something is firing wrong or fuel is igniting somewhere it shouldn't be. Was it your pipes that were exchanged under warranty and has that noise started after fitting the replacement pipes? It's more of a futting noise than a proper back fire.
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Oh er, what a strange noise. Sounds like something is firing wrong or fuel is igniting somewhere it shouldn't be. Was it your pipes that were exchanged under warranty and has that noise started after fitting the replacement pipes? It's more of a futting noise than a proper back fire.
I think the vid sound quality is poor it is really banging believe me
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For each of the 1 and 2 carbs separately, with it warmed and idling, incrementally turn the idle airscrew from virtually closed to about 4 turns out in quarter turn movement to see if and what changes you get.
Does it make a difference? Good or bad? Which gives the best running, at what position ?
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Doesn't sound like a "normal running problem".... has the cam chain been off at some time? are you sure the valves are timed correctly??
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That sounds more like a valve sticking open and clacking shut
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Could it be that the cam cover was not fitted carefully at some time and a valve is slightly bent?
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Could it be that the cam cover was not fitted carefully at some time and a valve is slightly bent?
I don’t think so but you never know, as I have said before in this post this started after a head gasket change but I am sure I fitted all back ok and I have done head off a few times now
Doesn't sound like a "normal running problem".... has the cam chain been off at some time? are you sure the valves are timed correctly??
Yes but double checked valve timing
Plus what are the odds of this happening only on 1 &2 only and equally the same
As I said it’s getting shipped off to a good mechanic near me. If I spend any more time on it it will be the divorce courts 🙊🙊🙊
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Hope you get it sorted Paul - been following the thread and it must be so frustrating
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Apologies for blundering in here but I've got a couple of suggestions that I don't think have been mentioned yet. They're both a bit left field, but given how frustrating this can be, I thought I'd chuck them in for good measure . . .
. . . first, I'll apologise for not being familiar with the Boyer kit, but when you say it comes with a rotor, is that a replacement for the spark advancer cam mechanism or is it the whole mechanism that's replaced? I ask because if it's the former, you might want to check the springs on the spark advancer bob weights. If one has lost some of its tension it'll flick out at inappropriate times - especially at idle - and you'll experience symptoms not dissimilar to those you're seeing.
The second is more dramatic and hopefully a very, very rare thing, but check then end the rotor is mounted to for deflection/out of round. Get your guy to put a dial gauge on the crankshaft end, turn the engine over very slowly and check for round or play. Again, if it's out you'll get some funny running and like I say, it's a bit out there . . . but it won't take five minutes to check when set up.
I can't take credit for any of this stuff. I learned the first one the hard way over the course of about 8 years working on and off on a project - it drove me the same kind of nuts you're experiencing and no mechanic near to me could figure it out either. Ultimately, Mark Paris (HondaMan on the US site) came to my rescue, and the crank suggestion came from reading his book.
Good luck.
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. . . first, I'll apologise for not being familiar with the Boyer kit, but when you say it comes with a rotor, is that a replacement for the spark advancer cam mechanism or is it the whole mechanism that's replaced? I ask because if it's the former, you might want to check the springs on the spark advancer bob weights. If one has lost some of its tension it'll flick out at inappropriate times - especially at idle - and you'll experience symptoms not dissimilar to those you're seeing.
Good luck.
Boyer replaces the spring advance retard mechanism completely and electronically advances the ignition above 4,500 rpm. Dayna S system, does utilise the mechanical advance retard system.
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Dropped bike off at local good reputation mechanic today, he thinks it’s blocked idle circuits/pilot jets so he is going to strip and clean carbs again and see how it goes
If that fails he is talking about doing a leakdown test etc
Let you all know how it goes
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Ok so local mechanic who has a good reputation has had bike for a day and is convinced this is a valve problem. Says he has heard similar sounds/symptoms on other bikes down to slightly bent valves that stick when warmed up.
Am now thinking that maybe I have accidentally slightly bent the 1 and 2 exhaust valves when I reassembled after the head gasket change.
This all seems logical as this problem only started after the head gasket change and am sure nothing else was changed, valve timing is correct.
Also thinking back I seem to remember I had a bit of a struggle getting the rocker cover to go on back easily even though I thought I had wound back the adjusters as far as I could.
Started another thread now as this is getting off track
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Ok so local mechanic who has a good reputation has had bike for a day and is convinced this is a valve problem. Says he has heard similar sounds/symptoms on other bikes down to slightly bent valves that stick when warmed up.
Am now thinking that maybe I have accidentally slightly bent the 1 and 2 exhaust valves when I reassembled after the head gasket change.
This all seems logical as this problem only started after the head gasket change and am sure nothing else was changed, valve timing is correct.
Also thinking back I seem to remember I had a bit of a struggle getting the rocker cover to go on back easily even though I thought I had wound back the adjusters as far as I could.
Started another thread now as this is getting off track
If you have bent a valve whilst putting the rocker cover back on, it’s possible you’ve cracked a valve guide as well. I know because I did it! A very costly mistake.
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If you have bent a valve whilst putting the rocker cover back on, it’s possible you’ve cracked a valve guide as well. I know because I did it! A very costly mistake.
I guess with these bikes its all down to experience, if this turns out to be the cause as you say an expensive but very good lesson learned