Still Running like a dog!!!

[K2-K6]

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?

[Johnwebley]

can I make a comment,


  the coils should connect to plugs 1 and 4 ,and 2 and 3

 its to do with piston position

[paulbaker1954]

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

[K2-K6]

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. 

[paulbaker1954]

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 !!!

[paulbaker1954]

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

[K2-K6]

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.

[paulbaker1954]

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 🤞🤞🤞🤞🤞

[hairygit]

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

[Erny]

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

[Trigger]

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 

[AshimotoK0]

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'.

[paulbaker1954]

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

[K2-K6]

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 

[paulbaker1954]

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