Irregular idling speeds?

[BeemeR18]

Only recently I have noticed that when starting with the engine cold, the idle is very irregular... Does this quite often, the RPM sometimes drops to 600-650 then back up to 950. The whole bike shakes really bad.

Sometimes I just re-start it but nothing has changed so I'm not sure what's causing it?

 

[Rufus]

Doesn’t sound right. If still under warranty take it to a dealer to check it out and run a diagnostic check for fault codes, If you find out what’s causing it update the thread because it’s useful info for everyone.

 

[Anibal]

Indeed does not sound right for a new machine.
In my experience (mainly with carburettors engines) the surge is either carburettor’s injectors needs cleaning - not your case) poor fuel quality, fuel pump not working properly, fuel filter dirty, vacuum leak, air filter dirty, dirty spark plugs and dirty distributor.
You see, these are not difficult tasks and one could take a few steps back and think where you last filled up your petrol tank, whether you ride on dusty conditions etc and maybe pinpoint the root cause and take action.
I would say you should take it to the dealer but I am trying to share a general rule of thumb to put your mind at ease and give you an idea. With all these fancy electronics thrown at the bikes these days, chances are none of the above applies and all it needs is a software update to tell the fuel pump to behave or send the correct values to the plethora of sensors that control emissions and what not, which could have an effect on the way the bike idles.

 

[Star-Lord]

Only recently I have noticed that when starting with the engine cold, the idle is very irregular... Does this quite often, the RPM sometimes drops to 600-650 then back up to 950. The whole bike shakes really bad.

Sometimes I just re-start it but nothing has changed so I'm not sure what's causing it?

What's the year and mileage of your bike? I'm guessing this is a new observation, since purchased; have you made any recent modifications to your bike?

 

[Ulrich]

Mine did something similar ... clearing the 'learned values' and having her re-learn it cleared that up.
.. just my 2¢

 

[BeemeR18]

Bike is a '21 FE model with just 3K miles on the clock. Been using premium petrol (99+) and no mods at all, 100% stock bike..

 

[Anibal]

Take it to the garage mate, it is probably something silly but it is not normal. They should be able to diagnose the issue pretty quickly. Keep us posted and best of luck.

 

[Keehn]

Mine did something similar ... clearing the 'learned values' and having her re-learn it cleared that up.
.. just my 2¢

Ulrich,

Our bikes need to LEARN new valve clearances after adjustment?

How does one go about teaching said bike about said adjustments? I have a GS-911 FYI.

Mike

 

[Ulrich]

Ulrich,

Our bikes need to LEARN new valve clearances after adjustment?

How does one go about teaching said bike about said adjustments? I have a GS-911 FYI.

Mike

No no no!! ... not valve clearances!! that is a mechanical adjustment ... what I am talking about are the mixture, idle and ignition timing values that are saved in the ECU, I don't remember of the top of my head where theses resets are in the 911 menu ... but I think it is somewhere in the engine controller section ... I will try some screenshots if I get a chance tonight ... I don't really want to reset mine ..but I should be able to show how to get there ... after the reset the bike will start with a basic mixture, idle and ignition timing setting and then slowly advance these settings towards more ideal settings until the ECU thinks that is as good as it gets ... roughly explained ... but as the ambient temperature changes these values should readjust ... but sometimes they won't (don't ask me why) and then you can end up with a bad idle or hard starting. Actually the hard starting was the reason I had to reset mine ... I had a no-start condition off and on ... and the reset cleared that up.

 

[valkraider]

I feel like this is just describing how “rock” mode idles.

 

[Keehn]

No no no!! ... not valve clearances!! that is a mechanical adjustment ... what I am talking about are the mixture, idle and ignition timing values that are saved in the ECU, I don't remember of the top of my head where theses resets are in the 911 menu ... but I think it is somewhere in the engine controller section ... I will try some screenshots if I get a chance tonight ... I don't really want to reset mine ..but I should be able to show how to get there ... after the reset the bike will start with a basic mixture, idle and ignition timing setting and then slowly advance these settings towards more ideal settings until the ECU thinks that is as good as it gets ... roughly explained ... but as the ambient temperature changes these values should readjust ... but sometimes they won't (don't ask me why) and then you can end up with a bad idle or hard starting. Actually the hard starting was the reason I had to reset mine ... I had a no-start condition off and on ... and the reset cleared that up.

I misread "values" as "valves".

My bad.

Mike

 

[Rufus]

No no no!! ... not valve clearances!! that is a mechanical adjustment ... what I am talking about are the mixture, idle and ignition timing values that are saved in the ECU, I don't remember of the top of my head where theses resets are in the 911 menu ... but I think it is somewhere in the engine controller section ... I will try some screenshots if I get a chance tonight ... I don't really want to reset mine ..but I should be able to show how to get there ... after the reset the bike will start with a basic mixture, idle and ignition timing setting and then slowly advance these settings towards more ideal settings until the ECU thinks that is as good as it gets ... roughly explained ... but as the ambient temperature changes these values should readjust ... but sometimes they won't (don't ask me why) and then you can end up with a bad idle or hard starting. Actually the hard starting was the reason I had to reset mine ... I had a no-start condition off and on ... and the reset cleared that up.

Curious. Over in the UK, especially over winter, we get plagued by regular overnight temperature swings from cold to mild that cause terrible condensation on garaged motorcycles. This year it’s been particularly bad.

Example. So I go into the garage, find the bike dripping wet (again) and feeling very cold to the touch because it’s been close to freezing for days but it’s now say 13 degrees C ambient and feeling damp outside. From what you describe I wonder if the ECU expects the bike to be the same temperature as ambient? But it’s not and it’s causing the starting mixture to be out of whack?

A couple of times over winter Ive started mine up (to dry it off and warm it through) and it’s sort of churned over coughed into life before it settles down into normal idle after 5-10 seconds. When the weather is ‘normal’ it fires up straight away every time.

 

[Ulrich]

Curious. Over in the UK, especially over winter, we get plagued by regular overnight temperature swings from cold to mild that cause terrible condensation on garaged motorcycles. This year it’s been particularly bad.

Example. So I go into the garage, find the bike dripping wet (again) and feeling very cold to the touch because it’s been close to freezing for days but it’s now say 13 degrees C ambient and feeling damp outside. From what you describe I wonder if the ECU expects the bike to be the same temperature as ambient? But it’s not and it’s causing the starting mixture to be out of whack?

A couple of times over winter Ive started mine up (to dry it off and warm it through) and it’s sort of churned over coughed into life before it settles down into normal idle after 5-10 seconds. When the weather is ‘normal’ it fires up straight away every time.

Not knowing exactly what the parameters are that are affecting the mixture (and/or timing advance) ... that is my theory as well. That would explain why (at least on mine) it comes back to what it should be relatively quick ...

 

[BMWmech64]

Only recently I have noticed that when starting with the engine cold, the idle is very irregular... Does this quite often, the RPM sometimes drops to 600-650 then back up to 950. The whole bike shakes really bad.

Sometimes I just re-start it but nothing has changed so I'm not sure what's causing it?

Sounds like the throttle potentiometer. It’s been some years, but when we serviced a bike, we would always check that. Try turning the ignition on,(don’t start the bike) twist the throttle to full open three times, then turn the key off, then start the bike.

 

[manhattan]

Only recently I have noticed that when starting with the engine cold, the idle is very irregular... Does this quite often, the RPM sometimes drops to 600-650 then back up to 950. The whole bike shakes really bad.

Sometimes I just re-start it but nothing has changed so I'm not sure what's causing it?

mine was doing the same thing...ride it!!
i now have 1700 miles and it purrs like a kitten.
i think it takes a while for these engines to loosen up a bit.
93 octane always

 

[JAMUSAURUS]

I find my bike likes shell 93. Starts well, pulls hard, and been getting better mileage over 91 octane

 

[BeemeR18]

Curious. Over in the UK, especially over winter, we get plagued by regular overnight temperature swings from cold to mild that cause terrible condensation on garaged motorcycles. This year it’s been particularly bad.

Example. So I go into the garage, find the bike dripping wet (again) and feeling very cold to the touch because it’s been close to freezing for days but it’s now say 13 degrees C ambient and feeling damp outside. From what you describe I wonder if the ECU expects the bike to be the same temperature as ambient? But it’s not and it’s causing the starting mixture to be out of whack?

A couple of times over winter Ive started mine up (to dry it off and warm it through) and it’s sort of churned over coughed into life before it settles down into normal idle after 5-10 seconds. When the weather is ‘normal’ it fires up straight away every time.

Yeah, this could be it. Also in the UK and the temperature/humidity in my garage is often different than outside.. Once warmed up, the idling is more stable.

 

[BeemeR18]

Sounds like the throttle potentiometer. It’s been some years, but when we serviced a bike, we would always check that. Try turning the ignition on,(don’t start the bike) twist the throttle to full open three times, then turn the key off, then start the bike.

Interesting - so I did try this, could hear the servo moving when actioning the throttle before starting up. When I did this first step, the idle then was a bit smoother, so it might have worked but could also be placebo, I don't know.
I didn't think it would be the throttle potentiometer (rheostat?) since the idle is handled separately in the throttle body - or at lease that was my understanding. So I expected this to be due to a sensor acting weirdly or the ECU expecting wrong values..

Bike is now booked at an approved garage at the end of the month, I'll see what they find.

 

[jr-111]

Interesting - so I did try this, could hear the servo moving when actioning the throttle before starting up. When I did this first step, the idle then was a bit smoother, so it might have worked but could also be placebo, I don't know.
I didn't think it would be the throttle potentiometer (rheostat?) since the idle is handled separately in the throttle body - or at lease that was my understanding. So I expected this to be due to a sensor acting weirdly or the ECU expecting wrong values..

Bike is now booked at an approved garage at the end of the month, I'll see what they find.

Did you ever get this figured out?