1200 GSA Rocking Sensation

[Japseroony]

Hi All,

I am now on my 4th GS/GSA and bought this one new from Allan Jefferies last March (09).

Ever since owning her she seems to have a rocking sensation when trying to hold a constant speed which is more noticably at high speed.

She has had the clutch recall done and is about to go in for the front brake line.

I mentioned this to Jefferies at her first and second service and they say they can't find anything!!

It is not wind buffing but feels like it or like the bike is backing off slightly when riding at a constant and very annoying.

Anyone had the same or can shed any light on this?

Thanks.

 

[bumpy]

How does it change if you pull in the clutch or change down a gear?

 

[Japseroony]

It goes away when I pull the clutch in but obviously the bike slows as you would expect.

I did think the recal I have just received could be for something to do with the ABS/TCS as its almost like something is cutting the power but not completely.

 

[polecat]

I have a 09 GSA and it's fine

 

[Japseroony]

I have a 09 GSA and it's fine

Thanks for that - really helpful

 

[Spout]

Are you sure it's not an 1150?

Sounds like the "surging" that occurs at constant (small) throttle openings where the engine management cycles between readings from various imputs (temp, O2, throttle etc etc) and finding the correct mixture. Never heard of it with the 1200s (but can be annoying on the 1150s).

Maybe you have a sensor on the blink?

 

[polecat]

Thanks for that - really helpful

Well I thought it was. Just making the point that it's not a common problem and is therefore probably just yours.

 

[red1]

Take it to Rainbow. Jeffries aren't a bad dealer but their service department doesn't seem as clued up as others. Plus they charge £15 for a loaner!

 

[rob mac]

The oxygen sensors run between 0.1 Volt (lean) and 0.9 Volt (rich). The engine management system will increase fuelling (run richer) until it receives a higher voltage signal feed back from the oxygen sensor, it will then back off the injector duration until it receives a lower voltage signal feed back from the oxygen sensor and then the whole thing starts again. This will happen at approx 6-10 times a second at cruise revs but different conditions cause different frequencies so you need to look for a match between the two sensors.

When everything is fine and dandy the frequency of this switching is fast enough that the corresponding injector duration is also fast enough that you can't spot it BUT when an oxygen sensor gets lazy (age/contamination/low build quality/sensor 0volt bonding) the time it takes to switch between high and low (the frequency) slows down as it takes longer to respond due to its poor condition. This means the injector duration takes longer to switch between lower and upper points - this then becomes noticable to the rider and manifests as a gentle increase and decrease in speed, especially noticable on flat roads (no other load interference) and at constant throttle (no other load interference).

If the oxygen sensor/sensors are your problem you will notice that the bike does not have this fault for the first few minutes of riding from cold as the engine management will be in "open loop" which is techy bollocky speak for not responding to oxygen sensor feedback request to lean off as the engine isn't up to temp so the priority is more fuel to help it run from cold.

No need to buy BMW oxygen sensors as they are standard 4 wire (one grey, one black, two white) and the thread is standard so just use universal ones from any motor factor or the really cheap ones off eBay if you dare go that low!!

The way to test them is with a dual trace scope and check that both sensors are running at the same frequency. If one is slower, well there's your bad man. BMW workshops can "see" the live data through GT1 test kit but as it "sees" the bike's engine management's interpretation (very sloooowwww) it's much better to use a scope directly on the sensor multiplug.

 

[Giles]

Are you on different tyres to those that you would normally use? (something new to you maybe like the roadsmarts that have been criticised for a gentle weave at speed ....??)

 

[Spout]

The oxygen sensors run between 0.1 Volt (lean) and 0.9 Volt (rich). The engine management system will increase fuelling (run richer) until it receives a higher voltage signal feed back from the oxygen sensor, it will then back off the injector duration until it receives a lower voltage signal feed back from the oxygen sensor and then the whole thing starts again. This will happen at approx 6-10 times a second at cruise revs but different conditions cause different frequencies so you need to look for a match between the two sensors.

When everything is fine and dandy the frequency of this switching is fast enough that the corresponding injector duration is also fast enough that you can't spot it BUT when an oxygen sensor gets lazy (age/contamination/low build quality/sensor 0volt bonding) the time it takes to switch between high and low (the frequency) slows down as it takes longer to respond due to its poor condition. This means the injector duration takes longer to switch between lower and upper points - this then becomes noticable to the rider and manifests as a gentle increase and decrease in speed, especially noticable on flat roads (no other load interference) and at constant throttle (no other load interference).

If the oxygen sensor/sensors are your problem you will notice that the bike does not have this fault for the first few minutes of riding from cold as the engine management will be in "open loop" which is techy bollocky speak for not responding to oxygen sensor feedback request to lean off as the engine isn't up to temp so the priority is more fuel to help it run from cold.

No need to buy BMW oxygen sensors as they are standard 4 wire (one grey, one black, two white) and the thread is standard so just use universal ones from any motor factor or the really cheap ones off eBay if you dare go that low!!

The way to test them is with a dual trace scope and check that both sensors are running at the same frequency. If one is slower, well there's your bad man. BMW workshops can "see" the live data through GT1 test kit but as it "sees" the bike's engine management's interpretation (very sloooowwww) it's much better to use a scope directly on the sensor multiplug.

That's what I meant, but I think "on the blink" sounds better

 

[harry]

Put it on the centre stand, start engine, ease into 1st gear, stand behind it and look at rotating wheel.
Look OK or not?

 

[Deleted account 190920001]

Just to say I can feel that on my 09 as well sometimes but not all the time. Feels like it has a miss now and again but doesn't sound like it. I always put it down to buffeting from a head wind or something like that but you have me thinking now.

 

[APW]

The oxygen sensors run between 0.1 Volt (lean) and 0.9 Volt (rich). The engine management system will increase fuelling (run richer) until it receives a higher voltage signal feed back from the oxygen sensor, it will then back off the injector duration until it receives a lower voltage signal feed back from the oxygen sensor and then the whole thing starts again. This will happen at approx 6-10 times a second at cruise revs but different conditions cause different frequencies so you need to look for a match between the two sensors.

When everything is fine and dandy the frequency of this switching is fast enough that the corresponding injector duration is also fast enough that you can't spot it BUT when an oxygen sensor gets lazy (age/contamination/low build quality/sensor 0volt bonding) the time it takes to switch between high and low (the frequency) slows down as it takes longer to respond due to its poor condition. This means the injector duration takes longer to switch between lower and upper points - this then becomes noticable to the rider and manifests as a gentle increase and decrease in speed, especially noticable on flat roads (no other load interference) and at constant throttle (no other load interference).

If the oxygen sensor/sensors are your problem you will notice that the bike does not have this fault for the first few minutes of riding from cold as the engine management will be in "open loop" which is techy bollocky speak for not responding to oxygen sensor feedback request to lean off as the engine isn't up to temp so the priority is more fuel to help it run from cold.

No need to buy BMW oxygen sensors as they are standard 4 wire (one grey, one black, two white) and the thread is standard so just use universal ones from any motor factor or the really cheap ones off eBay if you dare go that low!!

The way to test them is with a dual trace scope and check that both sensors are running at the same frequency. If one is slower, well there's your bad man. BMW workshops can "see" the live data through GT1 test kit but as it "sees" the bike's engine management's interpretation (very sloooowwww) it's much better to use a scope directly on the sensor multiplug.

Well this has got my interest as I am experiencing the same gentle rocking sensation only on flats and only on constant throttle. As I'm new to these GS thingies I just thought it was down to wind buffeting on the screen or something. It is a very gentle rocking sensation but it is there for sure and this explanation sounds like it could be the reason to me. will keep it in mind when I go in for the cam sensor recall an ask them to check......this is on a new 2010 bike as well

 

[seanb]

I had the same sensation on my 09 gsa that I had from new last year then same on new '10 gsa - always assumed it's just something that they do due to size, wind etc.