Low speed surging

[MisterB]

Hi all,

This week I went for a test ride on a 14 plate GS TE. Riding through towns at 30mph in 3rd gear the engine was surging - it just wasn't happy sitting at 30mph smoothly. Is this a trait on the LC GS in general or just the odd bike? I gather the LC GS has been improved each year so maybe the newest bikes are better?

 

[Engineer]

Should be fine at 30 in third, that's how I ride in town all the time.

 

[DRAIN MAN]

Never had any problems with mine, but a trip to Hill top does make the bike a lot smoother

 

[mrtee43]

Right, I'm going to ride mine up our nearest Hill top tomorrow to smooth out my bike.

 

[matchbox]

Did the bike you rode have the heavier crank? Not sure exactly when this was introduced but makes considerable difference at lower speeds and "trickling".

 

[CPJS]

Hi all,

This week I went for a test ride on a 14 plate GS TE. Riding through towns at 30mph in 3rd gear the engine was surging - it just wasn't happy sitting at 30mph smoothly. Is this a trait on the LC GS in general or just the odd bike? I gather the LC GS has been improved each year so maybe the newest bikes are better?

Mine (June 2014) was the same, it could not hold a smooth throttle even when set in cruise control, in the end I had it set up at Hilltop and that sorted it and more.
It is BMW's very lean mixture settings struggling to stay within Euro emission rules.

 

[ChazzyB]

That's interesting, my 2015 bike has a weird vibration through the bars and right foot peg, at low 30s in 3rd. It's like surging in as much as it comes and goes rythmically, lasts for a second, stops for a second.

 

[oldnfat]

I had the same issue with my 14 GSA, some are worse than others. In September 15 BMW issued a software update that amongst other things, was supposed to cure this issue and make the throttle overall less jerky goin on an off throttle (according to the service manager at Vines). Certainly my bike was better as a result but not perfect. Apparently there had been previous less successful attempts. All bikes serviced since then should have had the upgrade.

Others who have had afield remap from Hilltop have reported complete success in getting rid of this issue and making the bike generally smother and more responsive. When were your bikes last serviced?

 

[ShakeyGS]

Interesting.

My week old GS LC seems to be labouring at around 1500 RPM at 30 in 3rd gear so I generally use 2nd gear. Sounds better too

 

[ChazzyB]

When were your bikes last serviced?

6k service late last October.

 

[ChazzyB]

Interesting.

My week old GS LC seems to be labouring at around 1500 RPM at 30 in 3rd gear so I generally use 2nd gear. Sounds better too

I'm sure mine is doing just over 3K RPM in third at around 33mph.

 

[Engineer]

I'm sure mine is doing just over 3K RPM in third at around 33mph.

I think he was being ironic - if he wasn't they fitted the wrong gearbox to his bike.

 

[MisterB]

I'm sure mine is doing just over 3K RPM in third at around 33mph.

That sounds much more like my experience

Straight after testing the GS I took out a 15 plate RS - that was as smooth as silk which made me wonder if changes had been made to the later engines. Perhaps that's the heavier crank that matchbox mentioned...

 

[Caesi]

Riding through towns at 30mph in 3rd gear the engine was surging - it just wasn't happy sitting at 30mph smoothly.

at 20mph in 3rd yes, but at 30mph it should be very smooth

 

[ChazzyB]

I think he was being ironic - if he wasn't they fitted the wrong gearbox to his bike.

Yeah, wrong gearbox was my first thought, too...

 

[Wudee]

mine had the same. Running very lean. Have it hilltopped since and now so much nicer. Are your downpipes running very hot and therefore bright blue as well?

 

[Engineer]

Can some describe the full symptoms of 'surging' to me please?

 

[ChazzyB]

Can some describe the full symptoms of 'surging' to me please?

I wish I could. My GS vibrates where others' surge. When I rode Triumphs, other people used to complain about surging. They blamed O2 sensors, all sorts of stuff. Mine just vibrated badly. Perhaps I was lucky?

 

[Engineer]

I suspect that the term 'surging' is misused and this leads to confusion.

 

[MisterB]

What I meant by surging is that whilst holding a steady throttle position at 30mph in 3rd gear, the engine RPM was hunting a little either side of the RPM selected, resulting in the bike wanting to either accelerate or decelerate slightly. It did seem like a fuelling issue to me, the end result being the same as physically moving the throttle slightly. It just meant that the bike was harder work to ride through towns or filter with than I feel it should be. Sorry for the possibly confusing term - hope that clears up what I meant?!