Engine dies randomly while riding

[Eli69]

One of my old gs 's has an ignition switch that doesn't always make contact. It has occasionally turned off while riding. With no warning. Usually I just wiggle the key. All the electric stuff turns off. Just a thought.

 

[mcquillr]

Yes I was thinking of trying to bypass my ignition switch to see what happens.

 

[Gorminrider]

yes and the kill switch too....but if it's not electrical, you are going to have to go back to gas supply..

I rode the rest of the way home with the petcock in Prime mode but the engine died a few times along the way.

...any change when pulling the choke when the bike is slowing? would be somewhat a test for supply in the bowls themselves... floats hung up.. less likely, needles stuck which is more common for rubber-tipped than these..

I am guessing this is your setup then? Perhaps you got a defective kit-it's possible. and they have a note per wanting suppression plug caps too. So you might want to clean those up if they are the originals and/or get plugs that have suppression...The suppression stuff is part of the secondary's impedance and might affect heating at the coils if that were a thought...



..It might be in all that heavy black text I can't read but the kit seems targetted to later models than yours (80-83? GSX400 and GS450 ) but I can't see why it would matter beyond a slight difference in timing..not the issue here.

..if the coil is getting hot unless you can get one of those battery operated indoor/outdoor thermometers. The sensor would be on the coils or any thermom that saved Highest temppp...might do. ie part of the "always check the last thing you did" Especially so if the bike was running properly before you did it...but did it ever?

after I found someone had grinded down the lobes of my advance mechanism

 

[posplayr]

I'm wondering why you chose to eliminate one of the coils?
One of the reasons that Suzuki uses two coils is to give the coil sufficient time to recover. The faster the RPM the less time there is.

If you have one coil it has to run twice as fast which means it is not likely to fully magnetize the coil when the ignition is fired. It could be also causing the coil to get hotter than normal and further reduce its output.

I would go back to two stock coils and wire as per the manual. See if that keeps it from stalling.

 

[mcquillr]

yes and the kill switch too....but if it's not electrical, you are going to have to go back to gas supply.. ...any change when pulling the choke when the bike is slowing? would be somewhat a test for supply in the bowls themselves... floats hung up.. less likely, needles stuck which is more common for rubber-tipped than these..

Yes and I very recently rebuilt and cleaned out the carbs so I would suspect they are in good shape.

I am guessing this is your setup then? Perhaps you got a defective kit-it's possible. and they have a note per wanting suppression plug caps too. So you might want to clean those up if they are the originals and/or get plugs that have suppression...The suppression stuff is part of the secondary's impedance and might affect heating at the coils if that were a thought...

Correct, this is my setup. I did change my plug wires when I swapped my coil. I switched them out with 7mm Dynatek Copper plug wires. I can email Boyer-Brandsen and tell them what is going on. Maybe this is a defective kit.

..if the coil is getting hot unless you can get one of those battery operated indoor/outdoor thermometers. The sensor would be on the coils or any thermom that saved Highest temppp...might do. ie part of the "always check the last thing you did" Especially so if the bike was running properly before you did it...but did it ever?

It's definitely running better with the EIS installed. I couldn't physically set the advance timing with the stock setup. That's what led me to check the advance unit and to find that someone had shaved down the one of the lobes.

 

[mcquillr]

I'm wondering why you chose to eliminate one of the coils?
One of the reasons that Suzuki uses two coils is to give the coil sufficient time to recover. The faster the RPM the less time there is.

If you have one coil it has to run twice as fast which means it is not likely to fully magnetize the coil when the ignition is fired. It could be also causing the coil to get hotter than normal and further reduce its output.

I would go back to two stock coils and wire as per the manual. See if that keeps it from stalling.

My reasoning here is that no matter if you have one or two coils they both will always be working twice as fast so there shouldn't be any difference between having one or two. Am I misunderstanding how the system is working?

 

[Gorminrider]

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

Ok..but...how about the spark plug caps> using the old ones? Coils are not meant to run straight to the spark plug unless it's a lawn mower...You are aware that the original plug caps had 5000 ohm resistors in them? If you are running just straight copper with a different kind of cap without this xtra impedance....? I

or, it's been said that you can get the necessary impedance from the plugs themselves...a not-so-wild guess for your bike is that these should be NGK DR8ES-L the L being the indicator of impedance...
Mainly to say, I would not be running the bike without at least one or the other of these and both together works fine for me on an 81 with the stock ignition.

 

[posplayr]

My reasoning here is that no matter if you have one or two coils they both will always be working twice as fast so there shouldn't be any difference between having one or two. Am I misunderstanding how the system is working?

I'm not sure I see any reasoning.

If Suzuki could have made it work with a single coil they would have done that.

It basically gets down to this. A four-cylinder engine is two 2 cylinder engines. The main complication is how they are fired. A 4 cylinder fires twice every revolution of the crank. but because of wasted spark, there are actually double sparks going out (i.e. 1-4 or 2-3) A 2 cylinder also fires twice per crank revolution and it is also wasted spark.

So how can you fire twice per revolution with a single coil and get the same charge/saturation time to build up the magnetic feild?
The answer is you can't which is why you need two coils and is why the same ignitor will work.

 

[pdqford]

It basically gets down to this. A four-cylinder engine is two 2 cylinder engines. The main complication is how they are fired. A 4 cylinder fires twice every revolution of the crank. but because of wasted spark, there are actually double sparks going out (i.e. 1-4 or 2-3) A 2 cylinder also fires twice per crank revolution and it is also wasted spark.
.

Okay, I’m trying to follow along here.
On the four cylinder Suzuki the “paired” cylinders, I.e., #1 and #4 move up and down together and therefore can use what is referred to as a “wasted Spark” ignition system, where the companion plugs fire at the same time, but one is on the power stroke and the wasted spark is on the exhaust stroke.

Now I’m not familiar with this 2 cylinder engine you speak of, but I have had a Honda 305 Dream with a twin cylinder where both pistons move up and down together ( so it could use a wasted spark system in theory) and I have had a Honda 305 Super Sport twin where the pistons move up and down opposite of each other ( think John Deere Johnny popper style) and have unequal firing pulses, which would not support a wasted spark ignition system because of the uneven firing impulses.

So which style twin are we talking about?

 

[mcquillr]

Now I’m not familiar with this 2 cylinder engine you speak of, but I have had a Honda 305 Dream with a twin cylinder where both pistons move up and down together ( so it could use a wasted spark system in theory) and I have had a Honda 305 Super Sport twin where the pistons move up and down opposite of each other ( think John Deere Johnny popper style) and have unequal firing pulses, which would not support a wasted spark ignition system because of the uneven firing impulses.

So which style twin are we talking about?

I am under the impression that my bike, stock, uses the unequal firing pulses method. I'm pretty sure my bike has a 180? crankshaft. My original points system would fire each plug separately, not together.

 

[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.

 

[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 540? 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 540? 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 :apologetic:

 

[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