650 gtr won’t idle and misfiring

Check the voltage of the battery first if possible when it’s running

Turned off the battery wants to be 12.5 or so switched on no less than 11.9 with pump priming running ideally 14-14.5

With fuel injection if the voltage gets low the ECU will try to keep the main things running as long as it can which is why it will start to mess about, the fact the bike ran fine for a bit sounded like the battery was discharging so to me the first thing to check. Now it’s going to be a bit of detective work, it could be something as simple as a loose or damaged plug cap or coil or a sparkplug so that’s the next things to look at.

Doubtful that it would just be the gap, it is almost 99.9% going to be a bad connection or a failed electrical component

If  there’s no code it’s doubtful that it’s an injector, o2 sensor etc but a bad coil or sparkplug will not show up, the ECU is simply not that sophisticated the injectors don’t do anything when the ignition is switched on they only function when it starts.

Get a multimeter & tbh most checks are dead simple there’s most likely a manual on this site for the bike but most coils etc are a pretty standard resistance, check all the connectors you can find & by that unplug clean with contact cleaner spray cheap & easy to do, the fact the bike went for a test ride etc & was ok says it’s most likely something really simple.

It’s very difficult to diagnose over writing & not seeing the bike or knowing the ability of the owner regarding mechanical knowledge (I don’t mean this in any derogatory terms)

C means no fault,

Keep us posted, Simon knows his EFi babies inside and out lol, so follow what he says!

Could well be the fuel pump relay

A healthy fuel pump will always make a “whirring” sound as it stays continously on until you switch the bike off. Even as you turn the key on it makes that “whirr” sound.

Hmmm, fully charge the battery (with a bike charger instead of a car version due to excessive current damage)

Get fresh CR8E plugs , connect them to the HT caps , place them on the “unpainted” part of the engine such as a valve cover bolt, see how good the sparks are ?   Incase its not sparking strong enough to start ?

Also these stop sparks = Clutch Handlebar Switch (not recommended to bypass),  Stand Switch (if bypassed check contacts again) ,  Neutral Switch stays “Green” on the dashboard

Also , this sounds stupid, do you hear the fuel pump priming when the key turns on?

Using the “Share Link or  Get Public Link” option from either: OneDrive, GoogleDrive, Youtube (upload as UNLISTED!) ,  DailyMotion or other source to upload some video.

Paste it on the forum here, so we can watch what’s going on ?  – Ideally stand on the left side of the bike (where the pump is,  so the mic can pick up its priming noise)

But , do #1 & #2 before getting to the end of my comment.

Ps. test your stator & tell us the readings (service manual on this forum) , or if its suspicious, the bike won’t start without a good stator, it is the 1st thing it checks.

ECU primes fuel pump (unless its faulty or some other sensor in the bike is faulty , that means spending a lot of time with service manual to test every electric part you can find with a pocket meter) => Start Button is pressed => Solenoid Clicks to spin the starter motor => Stator Gets flywheel speed & pulses back to ECU => ECU, now does it’s magic to try start the bike assuming all sensors connected to it are saying “We’re good to go” or “not responding / poor response = Error Code / ECU shuts off ignition…    This is just a simplistic way i can describe the process but the service manual ofcourse has way more detail in how their EFi system works

The starting solenoid may be shot up.  Replacement time.

Though, not uncommon but it happens,  investigate the starter motor itself.   (Remove from engine,  place on floor ,  get jump leads,  put the bike battery on the floor)
I say this , as you may get sparks flying and wear gloves ,  do it away from the bike itself.   You will know if the starter motor is healthy and spinning strong.

If you press start on the bike itself , and the engine makes a “big thud” sound at the crank ==> check your sprag clutch  (behind the flywheel itself , but i hope not, as its means more work removing the flywheel!)

Good luck and try to take a break so you can enjoy your holidays and return to her with a renewed mind 😉

I had that before , it turned out that i had to sort out a few parts:

• Coils, Plugs, Caps in tandem
• The ECU wires had some oxidization, so had to clean up carefully and wait 24hrs to dry up
• Injectors just got replace (i couldn’t verify if they were faulty or not, but i just got new ones just to save future breakdowns, so new injectors advised!)

My last worry was the ECU itself but it would sometimes moan and say “Oxygen Sensor”   (lambda sensors on pipe) , it would run sweet once i got brand new ones, despite trying a few used sets from other donors.   The Daewoo ECU was frustrating to work with,  Delphi ECU is a little better but it takes less nonsense! So much as a clutch switch fault ,it refuses to even crank.

though, keep an eye on the “idle speed control unit”  , i can’t remember where but the manual mentions it.

Have a look at spark plugs (if they are brand new) , if they are wet = you have also possible stator problem if the coils aren’t sparking properly  (they need the stator & ECU to time the sparks)

Glad to hear its alive!!! 😍

You got it!  – If the coil is intermitent  (haywire or chaotic) it will behave as your video did.    I would replace the coils and try to use NGK leads and NGK caps  (The OEM Caps are too problematic to reliably conclude the matter as resolved)

If not , i would find a GOOD working OEM cap for now and use MAGNECOR HT wires alongside your new coils  (replace both)

I don’t know what your local stores are like in Australia , but browse the shop on this site and see if one of our coils matches your bike  (Hyosung makes different ones based on ECU,  ie. Delphi takes Delphi coils which we have started to list this week) ,  or an NGK wholeseller locally  and show him a picture of the NGK caps we stock up , that’s if you are in a mega hurry

WhyGoStock does similar if you want to use a US source ,  i rarely mention other sources like HyoAU, HyoNZ , HyoEU etc as they are the same design , same scammer that loads of people have complained about.

Magnecor HT wires are common on Amazon UK, so it should on Amazon AU ?

If not send us an email if need anything from us.

Or , try a local salvage breaker and go to their bikes in the yard that may have 2nd NGK caps on them  (just avoid plastic caps as they WILL crack),  and possibly a Hyosung that has the same coils as you, take a meter with you and test their resistance if they allow it.

It’s the Xmas rush & new years, so things are a bit slow in UK even to ship stuff abroad ourselves, if you don’t mind the extra wait.