Rising and erratic idle when warm

[YngveRT]

Hi all.

My first post here. I've been lurking for some time, but joined today as I realize you also have a RT section!

I am about to finish a 100 000 service on my `08 1200RT.

New plugs, checked valves, TB sync was fine at last service.

However, over the last two years, the idle RPM often climbs as the engine temp rises. Often up to 2000 rpm, but also sometimes higher. Forcing the throttle roll forwards helps, but usually the idle rises again regardless.

I adjusted the slack in the cruise Control cable as it was a bit thight. Bowden cables seems loose enough, and I also slackened them all the way to see if it would make a change. With the ignintion on, and not running, I can clearly hear the closing click in both trottle bodies.

So, what do you think? Can this be caused by dirt inside the throttle bodies?

 

[1964Hall]

It doesn't sound like we have quite the same problem, but my 76000 mile 2007 RT has a hanging idle.
If I close the throttle it wil reduce revs but hang at about 1500 revs for a second before dropping to 1100 idle.

I changed the steppers in case they were tired, no difference

What about an air leak or perished inlet rubber causing your raised revs?
.
\v/

 

[YngveRT]

... What about an air leak or perished inlet rubber causing your raised revs?
\v/

Hi Hall,
there could be an air leak somewhere. I will look into that, but rising /erratic idle sometimes can be eliminated by rolling on and off the throttle. Well, at least this procedure worked in the past, now it dosent work so well anymore. Restarting the bike also worked better in the past..
I probably will end up at the BMW dealer to have this sorted out, but I don't fully thrust them on finding the culprit either..

 

[1964Hall]

Well, keep us posted, be good to find out what the. Problem is.
\v/

 

[YngveRT]

Problem fixed? No closure!

I spent yesterday out in the sun trying to get rid of my rising and erratic idle.¨

I have not taken my RT for a ride afterwards, but the idle settled down nice even if the engine temp rose.

I found a small leak on the left carb to inlet gasket, but since it seemed to push the start-gas out instead of sucking it in, I decided to leave it alone.

I found however; a too tight throttle wire between the distributor box and the TB on the left side. Wanting to start from scratch, I loosened the wire going down to both TB's.

I then hooked up my GS 911 with the latest alpha software on my computer and started with an idle actuator calibration.

Then I wanted to continue with the synchronisation, and thus pressed the button for Lock idle actuators. Seeing that the engine needed to be off in this procedure, I obeyed the prompt on the screen and did this, BUT, I had not enough battery power to start the engine up for the synchronisation process!!. What was wrong? The battery is new since last summer, and has mostly been sitting on maintenance charge at room temp. this winter. It has been installed on my bike for the last three weeks, and the ambient temp has been around zero C, but it has been hooked up to a BMW charger all that time.

I put the bike on charge for 15 minutes, and it started up fine.

I then gave up on the GS 911, (a bit suspicious that it had messed with my battery charge), and I continued to sync the TB's.

Now comes the second surprise; I found it almost impossible to bring the carbs out of sync! No matter how I played around on both sides, there where not much of a change on my Twin max, at either RPM!

So confused, and a bit feed up with the whole sync. affaire, I only made sure that the left tight cable between distributor box and TB was not too tight, and put the fairing back on.

So, I do not know why my battery faded so fast, and I don't know why the engine seems to run fine afterwards. Only a proper test un will confirm that it is in balance, but it does not longer rise at idle.

It also shows a full tank, whereas prior to hooking up the GS 911 it only showed 3/4 full. (I did not realize the GS 911 tops up your tank, but I'm not complaining)


So, to the academy; Any comments?

What happened with my sync?.

Why was it so hard to get it out of sync when I had both cables (on both sides) adjusted way off?

Is the Idle actuator calibration the really important factor to this seemingly good sync result?

How did the GS 911 manage to add extra fuel to my tank? :burpletsgto:

 

[1964Hall]

Any news?