First two cylinders not firing Help

[Januik12]

Any suggestions off the top of anyone's heads as to why before I rip it apart and troubleshoot?
Bike has around 19k miles

My initial guess is ignition coil, bike ran great last week, did seem to misfire a little in high rpm, I assumed it was cold because it cleared up.

Help? Suggestions? I know it's the first 2 cylinders because the headers are ice cold and the other 2 aren't.

[CB700S]

Hm, if the coils are wired up like traditional Honda, doesn't one coil fire 1-3 and the other one fires 2-4? If so, I don't think the coils are at fault. You can check primary and secondary resistance of course, but the chances of both coils failing on their first of two cylinders is pretty small.

Edit: Okay, it's a little different - I just checked the service manual. On the 919, one coil fires 1 and 4 and another one fires 2 and 3. So it still applies - you would have to have both coils fail to lose 1 and 2 simultaneously. Check your wiring to the coils, ECU and both the cam and crank position sensors. I suspect it is one of the two position sensors that have failed (or the wiring has failed), most likely the cam position sensor.

[Pvster]

before you tear into the bike. check battery voltage, while it may be enough to start the engine, it may not be enough to fire both coils. so look into that first. once you've confirmed the battery is fine, check the coil and figure out which coil is not firing the 2 cyls and check all associated wires, etc.

[undercover919]

That would be my guess, but if I remember correctly I believe one coil fires cylinders like 1 and 3 and the other coil fires for 2 and 4. I'd check to see if plugs are fouled, check main ground under the tank.

[Pvster]

if its the first 2 cyls like you said, check battery FIRST. IMPORTANT! BATTERY FIRST!

[CB700S]

Yeah, low voltage *could* make it so that the coils take too long to charge to make both their first and second events per combustion cycle (they use waste spark). Have to be really, really low, though. Check that first, especially since it is free and easily done.

I'd be surprised if it was running at that point - most modern EFI systems have a critical voltage below which the computer doesn't even attempt to run the engine simply to protect components. That voltage is usually well above the point at which coils won't charge in time to make both events per cycle.

[mrhonda1987]

Did you recently do spark plugs or Pairs removal? Maybe you've got the wires switched around.

[undercover919]

wow... looks like I was beat by a few people lol.. always glad to see how fast a response is here

[Pvster]

Originally Posted by CB700S

I'd be surprised if it was running at that point - most modern EFI systems have a critical voltage below which the computer doesn't even attempt to run the engine simply to protect components. That voltage is usually well above the point at which coils won't charge in time to make both events per cycle.

actually you'd be surprised at what CAN run with low voltage from a battery. it just wouldn't run well. my vlx is notoriously known for running on 1 cylinder (the front) if the battery voltage is too low, its a very common issue for that line. many other EFI motors show different quirks when voltage is not ideal but can still run. another example is my 2000 jeep Cherokee. it'll do a slow start and fire up but wont hold it's own idle if the battery is low.

it all depends on what is wired in first to get the voltage before something else does. EFI motors are more sensitive and if you're under the ideal total voltage needed it'll show quirks while running.

[CB700S]

Originally Posted by Pvster

actually you'd be surprised at what CAN run with low voltage from a battery. it just wouldn't run well. my vlx is notoriously known for running on 1 cylinder (the front) if the battery voltage is too low, its a very common issue for that line. many other EFI motors show different quirks when voltage is not ideal but can still run. another example is my 2000 jeep Cherokee. it'll do a slow start and fire up but wont hold it's own idle if the battery is low.

it all depends on what is wired in first to get the voltage before something else does. EFI motors are more sensitive and if you're under the ideal total voltage needed it'll show quirks while running.

Actually, the majority of modern EFI systems that I'm familiar with simply have a critical voltage below which the computer won't fire the injectors or spark plugs to start the engine. With Jaguars, for example, if your rest voltage is below 11.7V, the computer won't even try even though it is still working just fine. Other makers have similar thresholds.

Mind, I'm not surprised that an EFI vehicle can run with low voltage - my old XJ6 will run on just 9V remaining on the battery albeit not well - but I'd be really surprised if the Honda ECU didn't have a protection circuit in it.

[Pvster]

but we're not talking about critical voltage here, we're talking about less than ideal voltage which is between 12-13.1 volts depending on brand. ideal voltage is 13.6 or higher.

[CB700S]

Yeah, but even at 12.0V, your coil rise time should be fast enough that you don't lose your first discharge event.

[nd4spdbh]

either way.... OP have you done ANY work in the past regarding plugs coils or wires?

If no... CHECK YOUR BATTERY.

coils are wired up outters and inner cylinders.... that is one coil fires cylinder 1 and 4... the other 2 and 3.... so its not like its a single coil problem.

[Pvster]

Originally Posted by CB700S

Yeah, but even at 12.0V, your coil rise time should be fast enough that you don't lose your first discharge event.

it ALL depends on what gets the voltage first compared to what gets the remainder voltage last. trust me on this. been there, done that.

[CB700S]

Originally Posted by Pvster

it ALL depends on what gets the voltage first compared to what gets the remainder voltage last. trust me on this. been there, done that.

Looks like on the 919, power goes to the engine stop relay and from there gets routed to the coils and only then to the PCM/ECU. So the coils should have the best chance of charging and firing at whatever voltage...

[Januik12]

Thanks for all the replies, my battery is fine and I've ridden 3 days or so since the last time the plug wires were off...going to check voltages and wiring now. Thanks again for the advise!

[Pvster]

Originally Posted by CB700S

Looks like on the 919, power goes to the engine stop relay and from there gets routed to the coils and only then to the PCM/ECU. So the coils should have the best chance of charging and firing at whatever voltage...

my question is this, which one draws more voltage?

[cmurphy84]

I thought it was 1 & 4 on one coil and 2 & 3 on the other.

Almost sounds to me like the plug wires for cylinders 1 and 2 got swapped.

What have you done to the bike lately?

[CB700S]

Originally Posted by Pvster

my question is this, which one draws more voltage?

At a guess, probably the coils. The PCM doesn't appear to be powering anything big other than the sensors, just providing switched grounds, and it's only on a 20A circuit. My non-EFI 700 uses a 10A circuit for the same thing and it's got less powerful coils than the 919 does.

[Pvster]

Originally Posted by CB700S

At a guess, probably the coils. The PCM doesn't appear to be powering anything big other than the sensors, just providing switched grounds, and it's only on a 20A circuit. My non-EFI 700 uses a 10A circuit for the same thing and it's got less powerful coils than the 919 does.

ok so what tends to happen is the coils has to share whatever voltage is left with anything else wired in series, likely the PCM. since the PCM takes less voltage than the coils do, 1 coil could still fire and the other doesnt due to insufficient voltage, or both coils could fire but 1 coil cant produce a strong enough spark.

however, reading more on this thread, i suspect that the person swapped spark plug wires because as far as we understand it, he's talking about cylinders 1 and 2. it's possible 1 cyl could not get enough spark and the other cyl on the same coil could. however, to say 1 cyl from each coil not getting enough spark doesnt make sense. nonetheless, electricals are strange things when voltage is insufficient, still check the battery, then check spark plug wires and trace it down.

[Januik12]

No I didn't swap the plug wires, everything on the bike including the battery were as they should have been. Something must have failed sensor wise. I recently did the PAIRs block off but rode the bike 3 days since then so I guess I'll just have to troubleshoot further

[nd4spdbh]

Its possible that you just didnt get the plug wires on the plugs all the way... i know they are a bitch to put on... and was the source of my problems back when i did a valve check and it was running on three cylinders.

[g00gl3it]

Originally Posted by nd4spdbh

Its possible that you just didnt get the plug wires on the plugs all the way... i know they are a bitch to put on... and was the source of my problems back when i did a valve check and it was running on three cylinders.

+1, push HARD on those suckers. You should feel them snap in.

[Januik12]

Yea did all that, I found another thread where a member had the same problem but there wasn't a solution in it so I messaged him to see what he found.

[nd4spdbh]

hmm ya... i mean if you rode it as it currently stands just fine a couple of times, it sounds like something just came loose. Check the two connections on both coils to the harness. as well as actually pull the plug wires off the plugs and put them back on.

[Dev]

1. What is the compression? You will chase your tail if you do not do something as simple as this.
2. Do I have a fuel or electrical problem?
3. For spark, I will remove said spark plug wire(s), install a good known plug that will jump a gap, ground that plug to the engine, hit the starter, note if I have spark? I have now eliminated spark and compression.
4. My fuel is next. I only have 3 variables, so it is one or the other, not both or all 3 in a way of process of elimination.

With fuel injection, there are sensors needing 0 to 5 volts. If 12 volts drop too low, say down to the low 11 volts, without that charging system kicking in to boost the volts back up, it will be difficult for the sensors to give their designated output signal in the 10ths of volts. Lets say a sensor needs 4.30 volts to send a signal the computer recognizes. If the main volts [12v] are low, it will be hard for the computer to send a spark in other words.

[honda ng gingsa]

Not the fabled hornet FPR? Mine was just one cylinder not firing though when I had to replace the FPR.