1200GS Engine misfire at low revs

[Twins rule]

My 08 1200gs has had a low rev misfire (hesitance) below 2000 rpm. Have had the various bits replaced (plugs coils etc) but stiil same. However i've notice that When Fully loaded and two up, it is almost perfect. Could it be Swingarm/shaft position related causing a loading issue that effects fueling control at low revs? Anyone had similar experience.

 

[RickG]

Can't see any way the loading would affect the fuelling except for the fact you've got more wieght and perhaps the throttle is slightly wider open to compensate. Is the bike actually misfiring or just feels likes it's fluffing with poor response until the throttle is slightly wider open? Does it pull OK in high gears at less than 2000rpm on a wider throttle? If so it's probably not ignition system related. I'd look at the throttle balance and do TPS reset if you've not already checked.

 

[Dinger]

I don't know whether it could cause the symptoms you described but each throttle body has a little rubber tit covering a wee tube. The rubber can and does wither and crack.
Might be worth a look.

 

[Pukmeister]

A 2008 bike is under manufacturers warranty, let the dealer fix it.

If they can't, take it to another dealer who can.

 

[BlueBird]

I HAVE

I have had this twice on my 05 1200.she got 40k up her now.

First time I changed the plugs and it went away,I thought it was coz I had stripped the cat and silencer guts out and was just harder on the plugs,colour of them looked good but a bit of ware showing on the centre electrode showing,
10k miles later it started again,it was going in to Mike Pearce for a full service so I asked him to change the plugs again coz I just thought it was them gone again.
Anyway Mike sez there was no gap on the exhaust valves on the side that was missing causing the missfire.
I had'nt had them checked in 14k miles though
Still the best bike I ever had

 

[Twins rule]

Can't see any way the loading would affect the fuelling except for the fact you've got more wieght and perhaps the throttle is slightly wider open to compensate. Is the bike actually misfiring or just feels likes it's fluffing with poor response until the throttle is slightly wider open? Does it pull OK in high gears at less than 2000rpm on a wider throttle? If so it's probably not ignition system related. I'd look at the throttle balance and do TPS reset if you've not already checked.

Cheers Rick. To me it does feel like fluffing rather than a misfire but it happens in all gears with very little throttle at less than 2000 revs. The bike just feels as if its choking slightly and not running freely somehow. When fully loaded it just feels like the engine is running with less resistance at all revs and is Happy (if you get my drift). Other than this the bike pulls and runs well while accelerating in any gear or any revs. Have had jefferies look at it 3 times and they've replaced throttle pos sensor and idle valves but still no joy. I suspect its fueling not ignition. Em?... whats TPS?

 

[Twins rule]

A 2008 bike is under manufacturers warranty, let the dealer fix it.

If they can't, take it to another dealer who can.

Jefferies are looking into the problem and have tried several things but still no joy. They are puzzelled by the prob and its booked back in for yet another go at sorting it. so far I've had great service from them and have confidence in them as a dealer but do you know of a better dealer / tech that could help?

 

[eupi]

Jefferies are looking into the problem and have tried several things but still no joy. They are puzzelled by the prob and its booked back in for yet another go at sorting it. so far I've had great service from them and have confidence in them as a dealer but do you know of a better dealer / tech that could help?

Hi there! have they tried to check the lambda oxygen probe besides the usual coils and hall sensor?

cheers

 

[RickG]

Em?... whats TPS?

It's the recalibration of the sytem to the throttle position sensor. If you have a quick search you'll find the proceedure.

Sounds like it's just not quite happy going from closed throttle to a teenie bit open.

Agree with eupi regarding lamda sensor etc.

 

[Twins rule]

Hi there! have they tried to check the lambda oxygen probe besides the usual coils and hall sensor?

cheers

Hi, They have done all diagnostic checks including lambda probes but have'nt entirely ruled them out. I've recently fitted a remus can and this made no difference to the symptoms. They may try replaciing these next?
Cheers.

 

[Twins rule]

I agree with you about throttle but they have replaced thr throttle position sensor and I assume they would automatically do the reset procedure then.
Note tho that when fully loaded the bike runs so much smoother at the bottom end and it really does'nt feel like the throttle position is that critical. its almost as if the transmission is introducing a cyclic load ( like a missaligned shaft or something that is not so pronounced when the swing arm is in a lower position. Note when 1 up, with no preload, the ride hieght is still higher than when loaded. Its wiered and really spoils what otherwise is a fantastic bike. I have an 1100s also and it runs flawless everywhere.

really appreciate your help Lads.
Ta

 

[RickG]

So you are saying the bike feels rough when it's one-up at low revs?

Is this roughness actually a misfire or are you describing a rumbling vibration below 2000rpm?

 

[Twins rule]

So you are saying the bike feels rough when it's one-up at low revs?

Is this roughness actually a misfire or are you describing a rumbling vibration below 2000rpm?

Yes, even two up without luggage. The ground clearence is significantly less when the problem is present(fully loaded), hence the swing arm runs in a slightly different plain which is why I wondered wether it was shaft loading related. Its More of a misfire than a vibe but Its not a distinct misfire that you can here, but feel it as it hesistates slightly. No Vibration. Sorry to be vague but its hard to describe. I have to ride very pricesely at the lower revs and its really frustrating, sometimes I just declutch and coast to avoid it. Note as soon as I declutch it runs sweet!!
Thanks again for your help.

 

[RickG]

Its More of a misfire than a vibe but Its not a distinct misfire that you can here, but feel it as it hesistates slightly. No Vibration. Sorry to be vague but its hard to describe. I have to ride very pricesely at the lower revs and its really frustrating, sometimes I just declutch and coast to avoid it. Note as soon as I declutch it runs sweet!!
Thanks again for your help.

I'm at a loss what to suggest. I was thinking that maybe your final drive was on its way out as that could explain roughness and why it's different when loaded compared to unloaded, but not anything that could cause a misfire and it would probably continue even if you declutched, which you say it doesn't. If you declutch to let it 'run sweet' I assume you are letting the throttle go and the engine is just ticking over?

If you run the bike on the mainstand in neutral and very, very gently open the throttle does it go from tickover to say 2000rpm without hestiation or is there a rough patch when the throttle has been just opened the smallest amount?

 

[Twins rule]

I'm at a loss what to suggest. I was thinking that maybe your final drive was on its way out as that could explain roughness and why it's different when loaded compared to unloaded, but not anything that could cause a misfire and it would probably continue even if you declutched, which you say it doesn't. If you declutch to let it 'run sweet' I assume you are letting the throttle go and the engine is just ticking over?

If you run the bike on the mainstand in neutral and very, very gently open the throttle does it go from tickover to say 2000rpm without hestiation or is there a rough patch when the throttle has been just opened the smallest amount?

It revs from tickover not too bad (tho not as smooth as Ive heard other Gs's), but if I run it in gear on the main stand then small throttle opening does seem to induce the fault and the backlash is extremely pronounced ( I mean sounds like a bag off hammers). In this situation it definateley sounds like a misfire.

 

[RickG]

but if I run it in gear on the main stand then small throttle opening does seem to induce the fault and the backlash is extremely pronounced ( I mean sounds like a bag off hammers). In this situation it definateley sounds like a misfire.

It will do. They all do that as the lash in the transmission plus the extreme angle of the driveshaft combine to set up the rattle the unloaded drivetrain as the parts alternately get accelerated and slowed. If you briefly put the brakes on (very gently!!!) it'll load up the rear wheel and hence the drivetrain and most of the noise will go away

If this noise is what you are describing as misfiring, could it not be the case that it's what you are hearing when you are on the road too and it's actually transmission noise - makes more sense of the loaded/unloaded differences?

 

[Twins rule]

It will do. They all do that as the lash in the transmission plus the extreme angle of the driveshaft combine to set up the rattle the unloaded drivetrain as the parts alternately get accelerated and slowed. If you briefly put the brakes on (very gently!!!) it'll load up the rear wheel and hence the drivetrain and most of the noise will go away

If this noise is what you are describing as misfiring, could it not be the case that it's what you are hearing when you are on the road too and it's actually transmission noise - makes more sense of the loaded/unloaded differences?

I wondered that, but when I apply the brake to offer very slight load to even moderate load and various throttle positions it makes tha backlash noise even worse! (like its going to dismantle itself!) and sounds like it is missing intermittently on one cylinder almost?
When fully loaded on the road, at NO point (any incline), rolling off/on throttle does it appear to misfire and it is smooth/effortless performance just like other GS's I've ridden 1 up. I dont think its the take up of backlash that I'm feeling. I'm sure if you rode it you would see what I mean.

 

[RickG]

If it's an 08 bike is it fitted with the optional ASC?

 

[Twins rule]

If it's an 08 bike is it fitted with the optional ASC?

No. Its completey standard.

 

[RickG]

No. Its completey standard.

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.