2010 TC rough / lumpy idle

[Jon P]

Hi folks, just acquired a mint, very low mile, looks like new, absolutely no rust, 30th anniversary. I‘ve owned a couple of hex heads previously (bought new at the time) but not had a TC.

Everything works great, rides absolutely lovely with the exception of a lumpy idle. (I’ve checked that the throttle cable is correctly routed behind the air intake tube). I’ve had a good look over everything including putting my Davida vacuum gauges on and they confirm that the cylinders are not balanced at idle but fine once the throttle is twisted. It’s quite apparent that the bike has not been messed with, meaning no modifications and I’ve checked all the electrical connections and plugs including looking for air leaks around the throttle bodies and exhaust headers.

So, not having had a hexhead before, my question is - is this just how they are?

Its also quite loud, but again, everything is clearly stock - not modified.

l live in the Highlands where there aren’t really any bike shops other than a local BMW main dealer and I get on real well with them so I could get some help there.

Just wanted to know your opinions.

 

[crimsondelo]

May be worth speaking to hilltop motorcycles, I may be wrong, but I think you can send them the ECU only. I may have had one of my GS' remapped and it certainly sorted some bits out.

 

[Mistacat]

The Idle stepper motors do not have an information feedback circuit, ( they do not no where they are).
First thing would be reset the idle stepper motors with a GS911 or similar.
Balance the throttle bodies just as the throttle movement starts to take effect, the idle actuators should be locked with a GS911 when balancing.

 

[Jon P]

The Idle stepper motors do not have an information feedback circuit, ( they do not no where they are).
First thing would be reset the idle stepper motors with a GS911 or similar.
Balance the throttle bodies just as the throttle movement starts to take effect, the idle actuators should be locked with a GS911 when balancing.

Thanks for your input. Surely, if the stepper motors don’t have any feedback how do they know what they are doing? Would their output not be based on things like temperature and rpm? Anyway, if it is possible to reset them, and certainly the imbalance suggests that they are not working together, then I’ll take it into BMW as I’m not sure where else I could get it looked at - I’m quite remote up here.

 

[Pukmeister]

I would highly recommend doing the modification to bypass the internal fuel filter in the fuel pump housing (basically a cast plastic strainer hidden inside that you carefully drill out) and add an external high pressure fuel filter. This cured my rough running symptoms on my old single-cam Hexhead when everything else failed.

I would also recommend replacing the stock fuel pump for a quality aftermarket pump (like a Quantum or similar) as they wear out/lose performance at anything over 30,000 miles.

If I bought myself another Hexhead these are probably the first things I would do to it.

 

[Slipperyeel]

Have you checked the plugs and coils?
A duff plug might only begin to behave under elevated revs. My last set of plugs were visibly suffering heavy wear at 26k miles.

The idle on mine is (to me, considering what the motor is) very smooth. So I guess you should be able to aim for that too.

Good suggestions above

Sent from my SM-G975F using Tapatalk

 

[Mistacat]

The output to the idle motors as you say is based on temperature, rpm, atmospheric pressure etc but this is information fed into the ecu and output to the idle stepper motors without feedback the stepper motors do not know where they are.
some say they reset every time the ignition is switched on but why is the option on the GS911 to recalibrate them available.
I believe it is a bit like the motors in the suspension units ( no feedback) they remember their calibrated positions until there is a glitch, the ecu does not know where they are so need to be recalibrated.

 

[Jon P]

So, dropped into my local BMW guys today and had a chat. They connected it up and confirmed no fault codes and they recalibrated the idle motors as a starting point. They suggest i should try it for a bit and see how I get on. If still not happy they said they would spend longer on it. I’ve only just got the bike, it is absolutely mint and with only 8000 miles - looks new. Looking through the bmw service history it’s never had a set of plugs so I’ve ordered those and I’ve put e5 petrol in. I’ll run it for a while

 

[Mistacat]

The TC tends to be hard on plugs for some reason, I change them every 12K miles. Modified a couple of sets of Denso Iridium plugs but they were u/s after 18K so now back on the stock NGK plugs.
I ran a set of NGK Iridium plugs in a 2009 bike for 0ver 40k miles and they were still good. Both bikes running an AFR of 13.8 to 1 so not as if they were running lean and getting hot.

 

[Jon P]

The TC tends to be hard on plugs for some reason, I change them every 12K miles. Modified a couple of sets of Denso Iridium plugs but they were u/s after 18K so now back on the stock NGK plugs.
I ran a set of NGK Iridium plugs in a 2009 bike for 0ver 40k miles and they were still good. Both bikes running an AFR of 13.8 to 1 so not as if they were running lean and getting hot.

Definitely no evidence my plugs have been changed, they may have only done 8000 miles but they’re 13 years old so they want changing anyway.

 

[botus]

on a hot engine with it running around 3 to 5 k rpm I squirted 300 ml of atomised 50 50 water meth in the airbox after the filter - idle is massively more stable afterwards

also run dipetane as that sorts most issues of ethanol filth ruining UK petrol https://dipetane.com/

 

[Jon P]

Changed the plugs, reckon they were the originals. Previous owner had the bike for 9 years during which time he did 2,500 miles. I now have a clearer picture of exactly what is happening. When cold, both cylinders are firing smoothly at idle. It’s only when it’s warm that the idle is lumpy. Once on the throttle it’s perfectly smooth again. Now I know from my visit to BMW yesterday that there’s nothing indicating a fault I’m thinking my symptoms may just be as a result of the bike hardly being used for 9 years. Other than the lumpy idle everything is super smooth and very responsive, the idle issue isn’t causing any problems so I’ll just ride it and see if it sorts itself out.

 

[botus]

its a BMW tractor closer to something you use as a generator - not a Merlin v12

 

[Buckingham]

remove the silencer & check the flappy valve is free to move - only takes a few minutes - you can hear the valve cycle when you turn on the ignition.

 

[Jon P]

its a BMW tractor closer to something you use as a generator - not a Merlin v12

That’s rather unkind, this is my 9th GS in 30 years and my 11th boxer, although it is my first twin cam hex head hence my question. A well set up boxer is a sweet thing

 

[Jon P]

remove the silencer & check the flappy valve is free to move - only takes a few minutes - you can hear the valve cycle when you turn on the ignition.

Yes, I checked that.

 

[Jon P]

Changed the plugs, they were clearly the original ones I took out as no record of them being changed in the service records. Still lumpy idle but sharper response out on the road.
Now I notice the air filter is the original, yes only 8000 miles on the clock but it’s 13 years old so new air filter ordered.

 

[Jon P]

All fixed now. I took it to my friendly BMW dealer in Inverness, they had it in for a few days which would allow them to work on the bike when hot and cold and thoroughly check it over. They could find nothing wrong but made some adjustments to the set up. They also suggested that I might want to try a fuel treatment as they suspected that the very low mileage suggests some varnish might be present within the fuel system. I tried the Motorrad product and now a few days later the bike is running sweetly and perfectly with perfectly balanced throttles. I was charged for half an hours labour. They were stunned by the condition, stating it could have just come out of the shipping crate

 

[timeandtide]

All fixed now. I took it to my friendly BMW dealer in Inverness, they had it in for a few days which would allow them to work on the bike when hot and cold and thoroughly check it over. They could find nothing wrong but made some adjustments to the set up. They also suggested that I might want to try a fuel treatment as they suspected that the very low mileage suggests some varnish might be present within the fuel system. I tried the Motorrad product and now a few days later the bike is running sweetly and perfectly with perfectly balanced throttles. I was charged for half an hours labour. They were stunned by the condition, stating it could have just come out of the shipping crate

Sounds like a good buy!
A mate and I had ours Hilltopped by Geoff. Both smooth as a very smooth thing from off the bottom.
Subsequently had a 650 Terra and 1190 Adventure R done - very pleased with all.