1200GS Engine misfire at low revs

[Twins rule]

Damn. I was getting desperate and hoping there may be a cable fault in the rear wheel ABS sensor that showed up only when the swing arm was dangling and fooled the ASC into cutting the engine.

Sorry mate, I'm all out of ideas. If the bike is as rough as you say it is, it ought to be test ridden by the dealer as it must still be under warrenty? If they are unhelpful try and get a second opinion elsewhere. I hope you get it sorted soon, let us know the outcome.

Thanks for your input. Much appreciated. The dealer has test ridden it and they say they could not detect a definate problem which suprised me but I know for certain there is a problem that needs sorted. If they cant sort it I'm going to have Mike kendrick have a look at it. If its not sorted soon I'll be selling it and maybe get another Gs. I have ridden several Gs's (and have a r1100s also) and they have not had this issue.
I'll give an update asap.
Cheers
Phil.

 

[RickG]

How about getting it on a rolling road/dyno rig and try strapping it down at the back to different levels until the problem shows up? Any loss of power due to a misfire ought to be evident as would any untoward mechanical noise?

 

[Pukmeister]

Could be due to spark advance under load giving better combustion compared to the part load condition.

I believe the GS senses engine load based on TPS angle, airbox pressure etc (but I may well be wrong) hence I would be inclined to suspect a faulty sensor somewhere fooling the ECU into giving an incorrect ignition curve when under part load.

Has the dealer tried new spark plugs, mini coils etc?

I think the driveline smoothness when loaded is coincidental due to the angle of the driveshaft when loaded relative to the final drive unit.

 

[Twins rule]

How about getting it on a rolling road/dyno rig and try strapping it down at the back to different levels until the problem shows up? Any loss of power due to a misfire ought to be evident as would any untoward mechanical noise?

Thats a good idea!!! I will wait and see what Jefferies come up with when it goes in on the 12 Aug. Will find a local dyno rig and maybe go there next?
Thanks again!

 

[Twins rule]

Could be due to spark advance under load giving better combustion compared to the part load condition.

I believe the GS senses engine load based on TPS angle, airbox pressure etc (but I may well be wrong) hence I would be inclined to suspect a faulty sensor somewhere fooling the ECU into giving an incorrect ignition curve when under part load.

Has the dealer tried new spark plugs, mini coils etc?

I think the driveline smoothness when loaded is coincidental due to the angle of the driveshaft when loaded relative to the final drive unit.

mm? Interesting. They have replaced coils and plugs and tps sensor already. One point I forgot to mention is that I can feel the problem be more pronounced sometimes when at higher speeds/revs in certain strong wind conditions, as if the air intake was also having an effect. So you may have a point there.
Ta.

 

[Pukmeister]

I can feel the problem be more pronounced sometimes when at higher speeds/revs in certain strong wind conditions, as if the air intake was also having an effect.

The electrical sensor within the airbox senses the air intake pressure to modify the engines running for differing loads or altitudes.

Maybe your dealer could fit a new one and see what difference it makes to the way the engine runs ? It wouldn't break the bank.

 

[Twins rule]

The electrical sensor within the airbox senses the air intake pressure to modify the engines running for differing loads or altitudes.

Maybe your dealer could fit a new one and see what difference it makes to the way the engine runs ? It wouldn't break the bank.

Cheers. I will mention this when it goes in next.

 

[Twins rule]

I hope you get it sorted soon, let us know the outcome.[/QUOTE]

Just an update. Well the bike was in jefferies for a week. It now rides much better 1 up and the misfire has all but gone?. It still feels not quite 100% low down but much better than previous and am happy with it now. What did they do?....They say that they went through it thoroughly but could not find anything conclusive .I wonder wether they have altered the mapping / mixture slightly to overcome the problem because the exhaust now pops back alot more on the overrun? but they say not.
Anyway off to spain next week so will see how it fares.
Thanks for your help.
Phil

 

[theop]

can it be the lean fuelling they all have to go through nowadays? I ve tried a friend's R1200R - the naked bike that wears the post 07 faster and leaner engine than my 55reg GS. The new engine feels revvier (i think it does a few revs more) and less inert - as if it carries a smaller flywheel, and it certainly feels faster higher up (not sure that wasn't the nakes feling and the air rush of the R though), HOWEVER it felt consistently less torquey and number than my bike between 3-4.5k, i.e where I normally ride.. I am told the fuelling through those critical mid revs is much leaner than the old motors...

 

[Twins rule]

can it be the lean fuelling they all have to go through nowadays? I ve tried a friend's R1200R - the naked bike that wears the post 07 faster and leaner engine than my 55reg GS. The new engine feels revvier (i think it does a few revs more) and less inert - as if it carries a smaller flywheel, and it certainly feels faster higher up (not sure that wasn't the nakes feling and the air rush of the R though), HOWEVER it felt consistently less torquey and number than my bike between 3-4.5k, i.e where I normally ride.. I am told the fuelling through those critical mid revs is much leaner than the old motors...

The R1200r has 109 bhp as apposed to 98bhp 0n your 05 gs. It is geared different and wont have the mid range torque of the gs. However it will be quicker overall when reved. I have an r1100s and it has similar characteristics to the R1200r. As for fueling issues, I've tried several other GS's and they were relatively smooth and better than my GS, tho it is much improved now.
The R1200r is a brilliant bike though. Much underated allrounder.
cheers.

 

[theop]

fair enough... Enjoy spain... I bet the bike will be much smoother 2k miles down the line...