Idle problem after restarting warm

[rsstler]

I got stuck in heavy traffic on the way into work this morning, damn tube strikes...

Traffic was not moving and my temperature gauge was rising so I turned the engine off. Restarted when traffic began moving, did this twice. On the third restart the engine began idling a lot lower than normal, around 700rpm compared to 1000 normally, it was barely ticking over despite being warm.

I had to use the choke (fast idle switch) to get the revs back up. Choke out half way got it back to normal idle speed, choke out full and it idled too high

Any ideas what caused this? Should I have left the engine running while stationery for an extended period?

It’s an 1150GSA

Not sure if it’s related but I’ve notice a intermittent exhaust/rattling sound on heavy accelerating and engine braking. Sounds almost as if the exhaust is on its way out. I suspect this maybe a red herring and not related to the idle problem

Thanks

 

[Steptoe]

Is it a twin spark model ? The main coil caps have a habit of failing or running erratically giving the symptoms you describe.

To check, pull off the two lower plug caps and see how it runs on just the main plugs. It may run on just one side or none at all.

 

[rsstler]

Yes, it is a twin spark.

Thanks Steptoe, I'll check the coil caps tonight.

If the main plug dies completely, can it still run on just the lower plugs? My understanding is it can run on the main spark plug alone, but not the lower plugs alone?

 

[Steptoe]

Yes, it is a twin spark.

Thanks Steptoe, I'll check the coil caps tonight.

If the main plug dies completely, can it still run on just the lower plugs? My understanding is it can run on the main spark plug alone, but not the lower plugs alone?

yes the bikes run on just the lower plugs, albeit with a lack of "urge" and rough idle.

 

[ELIMINATOR]

neil, if you were a bird, I'd marry you.

So much good advice, proffered so freely............................ yes, I am pissed.

 

[davegs]

Pissed visions

There are many men who've done that (not to Neil) and lived to regret it for the rest of their lives!

 

[MattW]

There are many men who've done that (not to Neil) and lived to regret it for the rest of their lives!

I've been pissed lots of times but I've never married a bloke (as far as I know...)

 

[kwallace21]

I had the exact same thing happen to my 1150 GSA this summer in France. Blistering hot day, sitting at 80mph on the motorway and pulled off at services for a drink. 20 mins later, started the bike and idle fell to around 700. I also had to put the idle on to keep from stalling. Once on the move it was fine and never did it again. Bike was well hot at the time. Someone suggested fuel vapourising in the bodies before getting to the engine, or something like that. All is well with it now though. Coils are tickety boo.

 

[rsstler]

Ok, to update... I followed Steptoe's advice and removed the secondary plug coils. The bike ran on both sides on main coil only, tho only with the choke on. It's still not idling correctly, prone to cutting out when idling without the choke, but the problem was not as bad as when I originally reported it.

I still think Steptoe is correct. I remember that when the problem occurred originally, one pot was running hotter than the other and the one exhaust pipe removed slightly more skin when touched...

Now I'm not sure how I identify which is the problematic coil

 

[denny]

I seem to have the same problem as the OP. Bike runs sweet as a nut when warm, however after filling up the tank or stopping for 20 minutes or so 90% of the time it will start immediately but run a little rough. Fast idle helps solve this but if I ride off straight away at slow steady revs it feels like its running on one cylinder, which almost caused an embarrassing drop while manoeuvring a tight corner. I've noticed that this can happen when starting her from cold too, as if it's not running on both cylinders.

As per Steptoe's instructions I've removed both lower plugs together, and one at a time, and she runs fine! Any idea what could be causing the problem?

 

[mspenz]

I had the exact same thing happen to my 1150 GSA this summer in France. Blistering hot day, sitting at 80mph on the motorway and pulled off at services for a drink. 20 mins later, started the bike and idle fell to around 700. I also had to put the idle on to keep from stalling. Once on the move it was fine and never did it again. Bike was well hot at the time. Someone suggested fuel vapourising in the bodies before getting to the engine, or something like that. All is well with it now though. Coils are tickety boo.

I had exactly the same thing happen on a recent trip to warmer climes, 30-35c heat and slow motorway/town traffic, temperature got up to 7 bars on a couple of occasions & I had to stop for a while to let it cool. After that for the rest of the trip the idling dropped to around 800rpm (on the counter) and it cut out a few times, usually at the wrong moment as well!

Once the overall air temperature dropped everything returned to normal and has been perfect ever since so maybe fuel vapourisation as you suggest?

I also had a stick coil problem recently, the bike would run but as Steptoe said 'with a lack of urge', the idle was ok but it backfired like a total b*****d!!

 

[mspenz]

Ok, to update... I followed Steptoe's advice and removed the secondary plug coils. The bike ran on both sides on main coil only, tho only with the choke on. It's still not idling correctly, prone to cutting out when idling without the choke, but the problem was not as bad as when I originally reported it.

I still think Steptoe is correct. I remember that when the problem occurred originally, one pot was running hotter than the other and the one exhaust pipe removed slightly more skin when touched...

Now I'm not sure how I identify which is the problematic coil

Run your bike in the dark (stationary) and see which down pipe glows more red, swap the coil to the other side then do the same again...the side that is hotter is probably the knackered coil as what you are seeing is petrol burning in the exhaust (not getting burned in the cylinder) causing the extra heat
Not a proven method but it's easier than skin removal