Engine dies randomly while riding

[Gorminrider]

yes 180 degrees -I expect it's like my 81 400. From the manual, a diagram so makes plain what posplyr is saying...firing at 180 degrees. for what it's worth, certain BMWs had what looked like a single coil too but I don't know how they fired...maybe we are looking at something called a "dual-output coil and I don't know offhand know what's inside these...but whatever is it getting hot? that'd be enough to start crying to the supplier, I think. Otherwise maybe move on to another idea, because if it's cooling enough in a minute for you to start and run a long time before it does it again, it wouldn't be my first suspect unless its getting hot.
180firing 540 to refresh.jpg

[pdqford]

Maybe the coil gets hot because it is being saturated for 540 degrees before firing the left cyclinder again??

[mcquillr]

Update: I installed an SH775 R/R and my charging system appears to be under control now. Also I bypassed my ignition switch using a kill switch and took it on a test ride. It hasn’t died yet but I want to be out longer next time to see what happens.

The coil I installed is a Universal 12V 4Ohm dual output coil from Dime City Cycles. I think it’s just the kind of coil you would use for a 4-cylinder bike.

So according to the diagram, yes it looks like the EIS is sparking during the 540º between positions two and five. However, I think this is just how the EIS was designed? I don’t think adding another coil would allow the coils to rest because the EIS would just spark both coils at the same time so you would end up with the same net sparking as you would with the single coil. At least that’s what is seems like to me?

[Gorminrider]

yes it looks like the EIS is sparking during the 540º between positions two and five. However, I think this is just how the EIS was designed

...because it has two pickups on the crank and therefore the black box is going to get a signal every 180 degrees...it'd have to be pretty tricky circuit to figure out how to stop firing the coils for the "correct" 540 degrees ...

but I'm hoping you found the easy and correct fix at the ignition or kill switch.

[mcquillr]

...because it has two pickups on the crank and therefore the black box is going to get a signal every 180 degrees...it'd have to be pretty tricky circuit to figure out how to stop firing the coils for the "correct" 540 degrees ...

but I'm hoping you found the easy and correct fix at the ignition or kill switch.

Same, but now I think I'm seeing what you were saying about suppression plug caps. I currently have NKG B8ES plugs on my bike (they have no resistor) but maybe I need the NKG BR8ES version with a resistor?

[Gorminrider]

yes, at least in my manual for my 81 400..I only have a pdf for yours and it's awful to thumb through

NGK DR8ES-L
this is the suppression plug NGK D8EA is plain-jane as I understand it...more info on the WWW of course..

I've used both and can't see any difference even if the suppression caps are on too. But I do believe the consensus is you MUST have either suppression caps or suppression plugs.

Cars have suppression in the leads, not the cap..(graphite sprinkled in glassfibre?) so you don't see it discussed the same way, but that kind of lead are not seen on our bikes...or lawnmowers either?

[mcquillr]

I took the bike out today (new R/R and bypass ignition switch) but still it dies. The plug wires I installed are apparently suppression plug wires so now I'm doubting this theory

[tom203]

It'll be nice to get this critter running right before snow arrives...way back you mentioned the replacement ignition coil , maybe you should try another in case this current one doesn't like this setup. Plenty of used dual coil Suzuki coils on eBay

[mcquillr]

Right? Ugh gonna have to ride into winter to make up for the lost time.

Changing the coil coil might be a good idea. Do you know what the difference between the expensive and cheaper coils is? Would that difference be relevant to my situation?

[tom203]

Not sure, but a new Chinese coil is unlikely to be made as well as the 40 yearold made in Japan ones. Maybe the B-B folks could recommend a certain coil known to work with this setup

[mcquillr]

That’s a good point

[Gorminrider]

I switched them out with 7mm Dynatek Copper plug wires.

The plug wires I installed are apparently suppression plug wires

so I'm assuming you really mean copper wires with a suppression plug CAP ? and that should be fine with any spark plug. this bike uses....

I'm not sure about this coil setup either but since it mostly runs fine I'm still wondering if your new setup is really the issue... ...you said it happens

while cruising or while moving slow. Sometimes when the bike is hot and sometimes after it has just warmed up.

Being able to start it right back up again makes it hard to trouble shoot... you could maybe attach some kind of indicator across the coil primary supply from the black box and see if that "signal" stops flickering while the bike dies..a pocket oscilloscope? haha... the dwell is going to be ..35 degrees or so so the flicker is about 1/6th of every ignition... I wonder if a digital Voltmeter or 12v led would react fast enough at anything above idle speeds? but something that did would confirm that it's electrical... and after you rechecked everything you can connection and power supply, you'd have to send the thing back.
Fuel still comes to mind...temporarily running out..the level in the bowl falling below where the jets can get it... when you stop and restart it recovers. Not sure what your exact process is to rrestart and since you've already tried "prime" on the tap , another way to test fuel while it's dying would be pulling choke-enricher ...if your carbs are the same as ours(ConstantVelocity) its tube goes deep in the bowl and would suck some gas up right away even if the float needles or the CV slide was hung up...

[mcquillr]

Thanks for these ideas. This past weekend I popped resistor plugs into my bike (NKG BR8ES) and miraculously the bike has not died yet, but I will give it a nice long test ride this weekend to see what happens.

I will keep you all updated.

[Gorminrider]

Good news! Thanks for reporting back.mcquillr. I'm a twin owner too so I'm particularly interested in your progress against the day my ol' "black box" dies.

[posplayr]

Thanks for these ideas. This past weekend I popped resistor plugs into my bike (NKG BR8ES) and miraculously the bike has not died yet, but I will give it a nice long test ride this weekend to see what happens.

I will keep you all updated.

This is a stretch, but a resistor plug presumably slows the discharge from the coils, which would mean during the cycle on recharge it might not have as far to go.

Basically, the voltage across a coil decays exponentially like in the link. It starts recharging at 1- exponential when the power is reapplied.

The fastest part of the curve is what generates the spark. That is right at Time=0 when the current path in the coil is broken.

After the spark jumps the gap, the rest of the curve is doing nothing but losing energy. If you can slow the process down, but still jump the gap you are retaining more power in the coil for the next cycle.

You are at the hairy edge if this is the reason and you need two coils.

https://en.wikipedia.org/wiki/Exponential_decay