The scourge of the surge

JayGee

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With 2500miles on the 12GS it's a great bike to ride quickly but still a bit of a lumpy old pig when riding slow. It's not too bad if I keep the revs over 3000, which is 2nd gear in a 30MPH limit but if I try to run at between 2000 and 3000RPM then it is uneven and has a bit of a surge around 2500RPM. Is this usual, does yours do it, am I riding it wrong (could be cos this is my first boxer)?
The dealer realoaded the fuel mapping at its first service but this still feels like a fueling anomoly.
Cheers JG
 
I never noticed this on the demo bike I rode a couple of weeks ago. Take yours back to the dealer and have them look at it again.
 
Surging..................?

I've done 1000 miles on our dealers demo, 3000 miles on my first 1200GS and just over 2000 on my current one and each one of them has been completely devoid of any surging.....

They've all pulled strongly & smoothly throughout the speed/rev range...........although my current bike seems to be even smoother than the other two.....

As with all large displacement twins, throttle body synch is absoulutely critical.......and I'm far from convinced that many techs in the BMW dealer network know how to check & adjust this correctly.....

Cheers

Dutch
 
I've heard one or two people with a similar sounding problem. Mines absolutely fine - it will rumble but ought to pull evenly throughout the 2k to 3k range. I usually use 3rd or 4th (if i'm just pootling around) in a 30mph.

Paul
 
Your engine is still new and tight. Although I experienced no surging, I did notice that the motor became more flexible and happy to run at fewer rpms as the miles piled on. I suspect that by 4k miles, most of your problems will be gone.

There is also the fact to consider that each motor design has it's own sweet and not so sweet spots in the RPM range. I try to learn where each engine in each vehicle that I own is happy and run it there, rather than trying to force an engine to operate where it is not happy.
 
There is a strange fuelling glitch on the overrun at about 2500rpm - most noticeable in 3rd when slowing e.g. for traffic lights. The bike tends to engine brake as normal until it gets to about 2500rpm, at which point it overfuels a bit resulting in a reduction of the engine braking effect.

I've not experienced any surging or anything unusual apart from this.
 
Tobers said:
There is a strange fuelling glitch on the overrun at about 2500rpm - most noticeable in 3rd when slowing e.g. for traffic lights. The bike tends to engine brake as normal until it gets to about 2500rpm, at which point it overfuels a bit resulting in a reduction of the engine braking effect.

I've not experienced any surging or anything unusual apart from this.
Click to expand...
That's just what I mean, rolling off the throttle it sort of surges or at least gets reduced engine braking at 2500, which if I trundle along around the 2500RPM it feels quite uneven as I go over and under the 2500RPM. It pulls quite smoothly from 2000RPM in 2nd, 3rd or even 4th but feels like an extra squirt of fuel goes in at about 2500 (on the overrun). Maybe I shouldn't have called it surging but what Tobers describes is just what I get.
It can be quite difficult in slow speed corners so usually I try and keep it over 3000RPM where the bike feels best. The low down pull has certainly improved as the engine has begun to run-in.
 
Its about 2500 rpm when the low speed engine balance management thingy cuts off and the throttle cables take over. May be worth asking your dealer to check the balance on the throttle bodies with the good old fasioned guages, NOT the BMW kit, cos it isnt sensitive enough. The guys at Mill BMW did this for me (and Georgia) and it made a huge difference.
Smooth as a pint of Guiness now, with no lumps :D (thats the bike - not the Guiness)
 
mine did it, but much better now after i had the first service at about 750 miles. now at 3000, its not exactly a smoothy at low revs but the on off on off engine braking response on a trailing throttle in the 2-3k range is no longer noticeable - much safer. would definitely not try to live with this, or try to ride around it by using the clutch to disengage the engine, when there is obviously a solution out there. given the height of the bike you dont want extra problems when slowing for slow speed manoevres.
Funny how some bikes do it while others don't.
 
A couple of days ago we balanced a 1,500 Klm old 1200 GS for it's owner. He was having exactly the same problem described above.

By very careful throttle body balancing the machine became eminently rideable around town at 2,000 - 3,000 rpm where previously it was so twitchy the owner kept it above 3,000 to make it manageable and safe.

This was after the first service, where supposedly this problem had been attended to!

I really do think that most BMW servicing is just that, servicing. Whereas, us backyard people, are into the kind of fine tuning that makes the difference between ordinary and a perfectly responsive throttle, unbelievable!

Mick.
 
finely balanced fuelling

I think Mick is quite right.

My 12GS came back from its 1st service with much-reduced overrun surging, but it's still there. Whether the improvement is from new fuel mapping or from (relatively coarse) re-balancing I know not. The surging still appears at around 2,500rpm on the overrun, but now I get it in 4th, which I didn't before; I can control it by changing the bad habits of a lifetime and abandoning lazy block down-changing for positive gear-by-gear downchanging (thereby avoiding the 2,500rpm problem point) - but I still prefer lazy if it's a safe option.

The other huge benefit of well-balanced fuelling is lower vibration. I had my previous bike (R1100RS) properly balanced and it was a revelation. No more numb thumb!

So all I have to do now is find a grizzled curmudgeon under some railway arch who knows about these things on a 12GS, and I'll be sorted. My previous curmudgeon has retired, unfortunately.

Chryso
 
Re: finely balanced fuelling

Chrysostom said:
I think Mick is quite right.

So all I have to do now is find a grizzled curmudgeon under some railway arch who knows about these things on a 12GS, and I'll be sorted. My previous curmudgeon has retired, unfortunately.

Chryso
Click to expand...
or take a trip to oz and have Mick do it !

Thanks for the feedback everyone, I'm taking it back to the dealers soon and try and get them to manually balance them. If that don't do it then I'll try one of the boxer independant service guys although I don't suppose they've come accross the 12GS yet- still shouldn't be much different on getting throttles balanced (should it?)
Cheers JG
 
Had my first service yesterday and commented to the dealer that during the 400 miles I did this weekend there was a little surge at low revs and I was getting a liveable but very noticeable numb right-hand using pro-longed (motorway) constant midrange revs, whilst still maintaining a light grip etc.

They said the engine felt very tight - which frankily amazed me as it was redlined for 12 of it's first 16 miles and I rarely dropped below 4,000 rpm after that!

They balanced the throttles for me and I have to say that the ride home was a real revelation - really smooth!

Incidentally I borrowed an R1150RS curtosy bike, which is extremely highly rated, RiDE satisfaction survey outright winner last year, and best sports-tourer this year. However by comparison it felt so cramped, heavy and very slow to steer - possibly too many motorway miles by previous owner wouldn't have helped.

I'd ridden every modern boxer from the last 25 years, bar the RS and the cruisers, and enjoyed them all. But with this particular RS I was sadly dissapointed in comparison with the 1200 - which felt far smoother, pokier and a real joy to ride.

I don't want too much clinical perfection (read: state of the art inline four) I enjoy a bit of character at real world speeds. I can perfectly udnerstand some owners perfering their character to clinical limit to stop at the 100 or 1150 boxer stage, but for me the 1200 is the perfect balance of the two. i.e. modern enough to simply 'work' like a quality product of this century, yet quirky and characterful enough to remain engaging and to make me smile. Rarely have I been so happy with a new bike :D
 
Yes absolutely! Warm it up for a few miles from brand new, then give it a good thrashing to get rid of that shiny power zapping glaze in the bores and invoke a good seal with the rings via pressure build up on the overrun etc. After that just ride it 'normally' for want of a better expression - we'll call that 4-5000 rpm for the remaining 588 miles :) then a bit more, as required, once run in.

My personal view is never leave a bike overnight or start it up on the side stand (especially an aopposed twin). Ride it as soon as you start it. Be smooth and gentle (up to 4,000 rpm) until normal running temperature, never labour it and don't permanently thrash it.

I've had about 25 bikes and never had an engine, clutch or gearbox problem; they all ran well, never used a drop of oil and made good power too.

Nb: I am fickle (or at least was until the GS12 appeared) and tend to have a new bike most years so don't reach the incredible miles that some of the forum guys have enjoyed with one particular bike, all I can report on is my own personal experience. And all I can say is that with modern engines you do more harm than good being too mamsy with them.

My dealer hasn't filled my bike with regular mineral oil (rather than synthetic) for nothing - they 'want' the engine to 'wear' in and non-synthetic helps this during the first 6,000. Still not convinced? ...

Well Honda always run a their 'brand new production' test engines for '24 hours at maximum revs' on a bench before passing an engine design as fit for purpose. they have 'very' reliable engines and in this months RiDE magazine which manufacturer beat Honda to be 'the' most reliable? ...BMW!
 
Couldn't agree more, this quirky bike is a hoot when ridden at sub 90mph and a real surprise not only to some sports bike riders but also to me. I just don't think a precision engineered engine should use oil nor should the oil level check be such a pain. However these are small prices to pay for such characterfull fun. With a smoother slow speed throttle (which I'll hopefully get soon) it would be even better.
Just topped my oil up with 250ml at 2550 miles (first service at 1000miles) which is more than I'd like but not too bad. I ran it in on a long holiday trip, two-up with luggage and lots of hills and twisties. I didn't stick rigidly to the 4000RPM limit but neither did I redline it, there's more to running in than getting low oil consumption. Since the first service it's been ridden hard as that's where the fun starts.
Cheers JG
PS the worst part of the bike is the crappy self cancelling indicators that always cancel when you don't want them to and when I am too busy to notice. Must be a good bike if that's my main grouse!
 
JayGee said:
That's just what I mean, rolling off the throttle it sort of surges or at least gets reduced engine braking at 2500, which if I trundle along around the 2500RPM it feels quite uneven as I go over and under the 2500RPM. It pulls quite smoothly from 2000RPM in 2nd, 3rd or even 4th but feels like an extra squirt of fuel goes in at about 2500 (on the overrun). Maybe I shouldn't have called it surging but what Tobers describes is just what I get.
It can be quite difficult in slow speed corners so usually I try and keep it over 3000RPM where the bike feels best. The low down pull has certainly improved as the engine has begun to run-in.
Click to expand...

Well, at little over 12,000 miles, mine no longer does that surge on deceleration at 2500rpm. I rode it around tonight trying to make it happen and couldn't. Just thought you'd like to know.
 
Thanks EMOTO, good to hear it goes away eventually but I'll still get it balanced and see if that improves things. The other solution is to ride faster:grndevil
 
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