[Dutch_rider]

Hey there! I'm new to this forum. I own a 2006 GT with 82.000 kilometers on the clock. Two years ago I bought this motorcycle off an acquaintance who had it sitting in his backyard for roughly 12 years. Obviously there had been a bunch of issues at first and the bike didn't run. I'll first list the things that have been done or replaced:

• Fuel pump (recall)
• Big maintenance service
• Used ZFE
• Used throttlebody (including injectors)
• Used radiator
• Converted the tankstrip to a floater off a K1300
• Exhaust off a K1300R (used)
• K&N filter
• Rebuilt ESA shocks
• ABS delete (with the RH electronics unit)

The list above had been done before recent problems started and the bike has been working perfectly fine with all these parts and upgrades.

• Used aibox off a K1300GT (upgraded model, including electronics)
• Recently updated software on the ECU

So the problems with my bike started last summer. This weekend the temperatures were around 25 C and I felt like cruising. During the first day, sometimes the idle would stick around 2K rpm, but after giving it a quick blip on the throttle it would go back to the regular 1K. It got worse up to the point where it would only idle at a steady 2K with a warmed up engine. That Sunday I rode to the beach, had a drink and when I started my K, the problem got worse. Now my bike would hesitate as well under 3K's while riding, above that the engine spun like there was no tomorrow. Obviously I tried to keep it above that line when I rode home.
After researching I found out about the Airbox issue. At first I contacted the dealership, but even just simply checking if my bike was affected with the crappy airbox at BMW by the chassisnumber took forever and I got impatient, so then I started to check this myself. Found an upgraded used airbox off a K1300, including the electronics. After that, it would stop idling at a steady 2K when warmed up, but the hesitation while riding under 3K rpm was still there. After that I thought maybe a software update would help. Now with the updated software, it will still ride like crap under 3K and idle rough even with a completely cold engine. It gets worse as the engine warms up. I've got the motoscan diagnostics app on my phone and I could see that (especially when the engine was warm) the Lambda value would sit around 0,8 below 3K rpm (revving freely, without load on the engine), above 3K it stabilizes at Lambda 1, which is the same at idle.
Yesterday when I wanted to check if all exhaust pipes would warm up evenly, the engine stalled after idling for about 10 seconds, followed by a ticking noise coming from the airbox.
I know I've not been the only one with these problems here and I've been on other forums as well to fix this. At this point I just want my bike to run like it did when I first fixed it and it seems like the people here have a whole lot more hands-on experience with the problems these bikes have, so I hope you guys can help me out! It's much appreciated.

 

[Kaus]

Hmm. So many choices ...

I'm assuming you're on a 2006 K1200 GT with ~82,000 kms on the clock? My thinking is to deal with and eliminate one problem at a time. Suggestions include:

• check the battery and its charge;
• check that the dual battery wiring harness upgrade has been done;
• check that timing chain tensioner upgrade has been done;
• check to freeplay on the throttle cables - if its too tight it messes with revs at idle / low RPMs;
• not convinced a K1300 R exhaust is "plug-and-play" into a K1200 GT (thought there was a regulator flap valve in the R series exhausts?). Regardless, check the seal between the exhaust header and the muffler for leakage;
• valve clearances should also have been checked at 60,000 - confirm from the 60,000 km service that they were in spec at that point;
• replace the spark plugs, if you haven't already;
• replace the O2 sensor with a newer NTK (or Bosch) version (I reckon this is a good call at 60,000 kms).

If none of these sort the low idle problem, then maybe think about the Throttle Position Sensors, coils, and double checking the ZFE.

Keep us all in the loop.

 

[Dutch_rider]

Thanks for your reply. I own the newer type K1200GT indeed and it ran 82k kilometers. I will check the battery voltages in the usual conditions, including the charging.
Excuse me, I only just meant the K1300R exhaust muffler. It is a straight fit to the original GT header. Bolts right up. The only difference is that on the GT, the rear mounting point is slightly higher I think. You only just have to move the big clamp that goes around the muffler by a few cm to the rear and you're golden.
At 80k the valve clearance has been checked. I requested this at the dealership, so I have a fresh start on maintenance. Fresh plugs, everything.
Which O2 sensor do you mean? The one mounted to the exhaust header?

 

[Kaus]

Hi Dutch_rider,

Thanks for the clarification on the exhaust muffler. I would still suggest checking the seal between the exhaust header and the muffler for leakage. Anything going worng there can mess with the O2 sensor readings which can then vary the air-fuel mixture instructions being sent to injectors. Good pick up too on the plugs - yes, well worth changing the plug to eliminate that variable too. And yes, I meant the lambda oxygen sensor mounted towards the rear of the exhaust header. Have edited my original response to include these in the list.

I should also add that there's a pile of threads in these forums on low idle issues, and a huge amount of knowledge - others will undoubtedly chip with other wise suggestions.

Happy hunting.

 

[Dutch_rider]

Is there any way I can check if the O2 sensor is okay? Maybe for resistance? Especially when hot (got a paintstripper laying around to heat up the sensor if necessary).
I'll check for exhaust leaks, that'd be an easy one.

I forgot to mention that the throttle cable play is in order I suppose. When I check the TPS value in the diagnostics, it says it's at 0% with fully closed throttlevalves. The engine only starts revving when I start to feel resistance on the throttle grip. There is some play on the grip before that point. Also when I start feeling resistance, I can see the percentage of throttle opening increasing in the live data.

So far I've seen TPS, CPS, faulty battery and the O2 sensor coming along in other threads. Is there any way I can measure anything about these sensors?
I might thought it could also be due to a faulty coil? Usually also occurs when the engine warms up. Tough one to check though with draining the radiotor and everything :/.

 

[Kaus]

There's not much to check on the O2 sensors. As I understand it the diagnostic units will just tell you that the sensor functioning, or its stuffed. My (limited) experience is that the older Bosch versions original to these bikes have a service life of 60,000 kms, according to the Bosch and other aftermarket websites. I changed mine over to a newer NTK version and it made a detectable difference to my low idle problem. Adjusting the throttle cables made a significant difference on top of that (mine were too tight - ie, not enough freeplay). Sorting the valve clearance seems to have eliminated the last of my low revs issue.

 

[Dutch_rider]

So when I tried to check if the exhaust was leaking (which it wasn't), the engine died after about 15 seconds. This really only occurs when the engine is cold. At first I thought it was the idle airflow regulator, but when I twisted the throttle grip, I could hear it actuating just fine. When it stalls, I hear a ticking nois coming from the area in front of the airbox anyway. It sounds like one of the actuators is unable to perform it's cycle and keeps repeating it without success. When I try to start it, it will crank and run, but throws out a few pops and stalls within a second or two. Then when I turn off the ignition and turn it back on, the bike will run once again. Still with rough idle though, without stalling any more.
I found some procedure to recalibrate the throttle position sensor. Probably it will take a week to be delivered. To be continued...

Edit: Now that I think about it, this whole situation with stalling in combination with the ticking noise is exactly what happened with the old airbox. I now start to think it might not be related to the airbox electronics, because those are all different now. There is this acutator directly bolted onto the throttlebody. Partnumber 7707608. What does this do? It's called acutator motor, throttle valve stop. Number 2 on the drawing.

 

[Beech]

It extends (actuates) Its solenoid shaft in first and second gear to keep the fuel rack from going to full fuel. Primitive traction control. It is possible to put 1mm spacer washers under the attachment ears, #4, and position it further away from the stop plate on the common rail that it hits. More power in those gears if it is desired. Just a hot rod trick though.

 

[botus]

It extends (actuates) Its solenoid shaft in first and second gear to keep the fuel rack from going to full fuel. Primitive traction control. It is possible to put 1mm spacer washers under the attachment ears, #4, and position it further away from the stop plate on the common rail that it hits. More power in those gears if it is desired. Just a hot rod trick though.

really ? never knew (sounds interesting if so).

I'd have thought its the idle stepper motor to modulate idle speed (its got one somewhere) - the idle stepper motor is a key one to recalibrate with dealer or after market tools just to make sure everything is where it meant to be. It just moves through it normal range and settles to its new default (takes 5 mins)

As for the bike's real TC it works off a difference in wheel speeds from the ABS sensors, more than x difference kill the power (not sure what it kills, ignition or fueling), is it this valve then ? the idea of ASR is rudimentary and you need to be in Sport to ride the bike, or its a catastophe of irritation. Or are you saying the washer trick gives Sport + ?

 

[Dutch_rider]

Interesting! I assume it only works as a limiter and doesn't do all that much at idle or slightly opened throttle?
I did indeed calibrate the idle air actuator when I installed the upgraded airbox. If needed, I guess the guys at BMW would have done it after the software update? When I first did it, it didn't make a difference though, unfortunately.

 

[Beech]

Don't walk away from your idle air valve at the bottom of the air box. That little thing can cause trouble. The computer does fuel control with some sensor inputs but this is just a mechanical upper end of the throttle stop, before the plates reach wide open. (which is also observed by the throttle position sensor on the right end of the rack rod.

 

[Dutch_rider]

I've come to this conclusion. It also seems to openup wide when you open the throttle over 20% or so. Ingenious system, but rather troublesome. With the engine not running, I can hear it operating at that point and with fully closed throttle.
I've received the O2 sensor today. Tomorrow I'll give it a go

 

[Dutch_rider]

No difference with another O2 sensor. I wanted to try the TPS from the old throttle body I had laying around, but when I wanted to put the bike back together, I found out the rubber grommets below the throttlebody are severely dried out and when I bent them, they show huge cracks. Not sure if they have gone all the way through, but now that I'm in there anyway, I'd rather have them replaced to eliminate them being the problem.
The TPS that came off the throttle body that's on the bike atm has some discolouration on the white part that holds the shaft. Don't know if that means anything, but the other one was just white. When I have the grommets in, I'll come back for an update on the situation.

 

[Corkboy]

Just joining the tail end of this discussion. Perished rubber can leave unmetered air into the engine, which can create issues like you're experiencing. There was an old trick with a combustible aerosol, sprayed around the area to see if RPM changes. Changing them out is definitely a good idea if they are suspect.

The throttle valve stop is a red herring (as you've deduced). All it does is extend out via a solenoid in 1st and 2nd gear if you go WOT, to limit the amount the butterflies open. It has no effect on idle or non WOT situations. And anyway, it prevents the bike revving, it cannot cause it to rev to 2000.

My other guess is, as Beech said, the idle air valve is the main cause of idle issues. If replacing the worn rubber doesn't do the trick, that's where I'd look next.

And you have already reset the TPS. (which as you've said, sits at the end of the rail. Number 6 in your diagram.). But I'd be interested if swapping it out makes a difference.
I notice that the part was changed according to RealOEM, in 2018. I wonder why?

And finally, after reading so many posts about idle issues, including idling at 200rpm, on the 2006 K GTs, I have yet to read of a definitive solution. My mate's bike, a 2006 GT, exhibits the same issues at times. For no reason it will start and jump to 2000 RPM and refuse to idle. He'll turn it off and on again and it may go back to normal. He's had all the work done, including new airbox and idle air valve.

Who knows ,you might be the knight in shining armor that finally resolves the issue with the 2006 Ks.

One other question I have, is that it has been suggested that use of Cruise Control also causes the symptoms to appear afterwards. Have you used cruise control?

 

[botus]

One other question I have, is that it has been suggested that use of Cruise Control also causes the symptoms to appear afterwards. Have you used cruise control?

that point made me think if the push pull throttle cables are set wrong - maybe a bit of steering lock can get things in a muddle as slop that is missing has even more effect on the throttle when a bit of lock is applied

 

[Dutch_rider]

I am aware of the trick. Usually I use brake cleaner for that. The severe lack of room on this bike to go spraying about to really determine if there is and if so where the leak might be, makes it just impossible. I'm also not in the mood to either fix some seperate fuel container with a pump and everything or make extended lines and wires.
Thanks for the explanation. Today I found out my memory was wrong, as I thought the actuator was on the other side of the throttlebody. Rather pushing it open than keep it shut for ever so much. No worries about that indeed. Seems like there's a newer version of that on the current throttlebody now anyway. Might do the ring trick next time I'm fiddling with the bike.
The thing with your friend might actually be the cruisecontrol actuator cable. Below the ABS unit on the left side of the bike sits the CC. The cable has a big rubber sleeve. You can pull that either forward or backward, I don't remember. Underneath that, there's an adjuster for the cable. If it's too tight, it will obviously keep the throttle valves opened by a little. I've had that problem with mine. Only have to take off the left side fairing to check, so maybe worth giving it a try.
For me, the only problem I'm still facing is the jerky rpm drops and rough idling basically. The 2000 rpm idling had been resolved by the upgraded version of the airbox. She hasn't done that eversince I installed it anyway.
I've been using CC all the time. Even now if I wanted to go for a ride, it would work perfectly fine above 3000 rpm. No other problems will occur while or after using it.

 

[Beech]

That rough idle is a bit of normal operation for a 1200. (driveability) It is one of the reasons BMW turned over an engine re design to Recaro in England to smooth out the engine, thus the K1300 was created. Years back I crashed my K13 in a hail storm. Needed the shifter welded and borrowed my friends K12 to ride to a large enough town to get it welded. I was in shock how poorly it ran in town, but on the road it was (is) a hot rod. It just is not a city bike at all.

 

[Dutch_rider]

That might be, but before the recent problems began last year, the bike had been spinning like a champ. Even down low in the revs and idle was way more steady than it is now. There's just something on the bike that didn't like the mid summer heat of last year, apart from the airbox. It doesn't feel like a mechincal issue and it gets worse as the bike warms up. Right now I'm just trying to systematically get to the cause by ticking of all the possibilities.

I forgot to mention that this afternoon I also measured the voltage delivered by the alternator, which was a steady 14,3V at the battery. To me that seems like the bike gets plenty of juice to keep all the electrical stuff up and running while operating.

 

[Beech]

Proper alternator voltage. As you describe the progressive idle problem is smack on the idle air valve. Maybe when you have the bike open remove it and do a little cleaning. Some sort of super fine quality lube besides silicone base might be helpful. (silicone and O2 sensors are a no go) I have a new one on the shelf for this but they cost 250 US $ . Not cheap for a guess. You have also convinced me that I'm ordering as set of rubber mount tubes for the throttle bodies to have on hand also.

 

[Dutch_rider]

Well the bike is all broken down to the throttlebody now anyway. I'll take out the valves from the airbox (also the PCV, just in case), give them a little check up and I'll see if I can find something to lube them up with.
The rubbers that connect the throttlebody to the cylinderhead aren't too expensive. Complete pain in the ass to get to, so probably after so many years it's not a bad precaution to replace them at some point. Especially when you're already down in there.