1992 Yamaha FJ-1200 ABS does not want to idle when hot. Splutters, misfires and dies.

[DutchFJ1200]

Morning chaps,

Been happening for a while now but more so when it gets hotter outside.

Starts good when cold, drives and pulls like a train. My drive home takes 30 mins through some heavy traffic and filtering. When stopped at a traffic light or when I get home to open the gate the bike starts spluttering, misfiring and dies.  At a a traffic light I have to keep the revs at or above 2000 rpm.

Have looked at various forums but nothing conclusive ranging from carb settings, vacuum leaks etc.

My bike shop guy has turned up the idle a bit and he thinks it may be the coils getting hot after a bit and might need to be replaced.

 

Any ideas ?

 

[NE0]

53 minutes ago, DutchFJ1200 said:

he thinks it may be the coils getting hot after a bit and might need to be replaced.

He may well be right Dutch. I had something similar years ago on my 400/4, that has twin coils under the tank directly above the engine. One of them was playing up especially in hot weather. Heat from the engine and warm air from the environment was too much for it and it would often play up in the summer months. A replacement solved the problem. mind you it did take a long time to trace the cause!!

Not expensive..

https://www.squaremotorcycleparts.co.uk/products/ignition-coil-yamaha-fj1200-fj-1200-1988-1994

worth doing for that price, and yours will be 32 years old already if original!!

 

[DutchFJ1200]

You Sir get the Platinum medal today    lol

Shoot.... thanks for the link.

 

I normally get my gear from Wemoto ...... they are double that price https://www.wemoto.com/bike/yamaha/fj/1200/1992/28776/ignition-coil

[DutchFJ1200]

Merry Xmas all,

Sorry for the late update. I was locked out of my account and getting back in is like trying to get into Fort Knox.

The saga continues.

Anyhoo, the el cheapo coils did not fit my bike so fortunately I could send those back.

Enter 2 OEM coils @ 150 quid a pop + installation.  Did it change anything ? ..... Nope.  Commuting home and sitting in traffic, filtering at slow speed and stopping for a red light from time to time and after a while it starts hunting, then spluttering so I have to keep the revs up so it doesn't die.

What I did discover with an infra red thermometer is that - if cylinders are numbered from left to right - when it was running but misfiring : 1 was at 220 degrees, 2 was at 150 degrees, 3&4 were at 290/300 at idle.  So cylinder 2 is not behaving.  WHY ??

Next move was to put new plugs in 1 & 2 because they might have been affected by the old misfiring/overheating coils.

The coils fire 1 & 3 and 2 & 4 so I have been told.  The coils can be ruled out because number 4 is okay so the thinking is mechanical.  Valve clearances, carburation or whatever else can go on down there.

I did tell the mechanic chappy that experimenting at my expense is no longer an option, but he agreed that if he could have to bike for a bit he would try to get to the bottom of this issue foc.  He is baffled by the whole thing as well.

 

I'm still riding the bike to work but I now have misfiring anxiety on the way home lol   If the traffic lights align and traffic is light and I can make it home in one hit without stopping I'm fine.

 

**if we get to the bottom of this it may not have been my coils at all ....... now that will be an interesting conversation with the guy**

 

 

 

Edited December 24, 2024 by DutchFJ1200

[Snakebite68]

No codes?

[DutchFJ1200]

On 12/24/2024 at 3:16 PM, Snakebite68 said:

No codes?

I don't think they had invented codes yet in 1992 

[NE0]

Happy new year to you Dutch, sorry to hear that those coils I sourced didn't fit your bike and you ended up paying out for an OEM set, which still didn't cure your problem.

I assume then that a 92 bike will be some sort of electronic ignition, bearing in mind my 78 DT does, albiet an early form. What's the carburation on it? is it carbs or fuel injectors?

If this was a car ,which back then were mostly fuel injected, and the coil pack has been eliminated then the culprit would likely be the ECU.  If it has an ECU then the fault codes are a series of flashes on the dashboard of cars from that era. You read them by putting in the key and counting the flash codes, which you then look up to find the corresponding fault code.

I'm not saying for one minute that this will apply to your bike, just that codes were around in the early 90's on many vehicles, and were the predecessors to the ODB2 that you find on modern vehicles.

Do any bulbs happen to flash/or LCD segments blink when you put the key in by chance?

[NE0]

Found you a service guide for your bike, looks like the ECU does give you fault code lights!! it states:-  In this case, the memorized fault codes can be identified by putting the ECU into the diagnosis mode and using a circuit tester or the warning light  page 13 onwards.

I think reading through it, the ECU does the ABS and Ignition, either way worth a read or showing to your mechanic.

We're not allowed to link to content elsewhere, so once you've had a look I'll re-edit my post and remove the link.

https://www.fjclub.dk/katalog/1991-FJ1200-Service-Guide.pdf

 

[NE0]

...and just thinking, whilst we don't want to lose you, have you thought of joining the FJClub and asking them for advice? someone else may have had a similar fault. https://www.fjownersclub.co.uk/

[Snakebite68]

Or, there's the expensive / buggeration option: When was the last time your valve gaps were done?