Idle speed

[TIV]

I am curious to know how fast you let your K75's and 100´s idle. If I slacken the adjusting screw on mine until it´s loose the idle speed will not go lower than 1300 RPM (hot). It is a wee bit to fast for my taste. I would think that around 1000 RPM would be more like it. Otherwise the bike runs perfectly IMHO.

It has been like this since I got it. When I got it few years back I took everything apart, cleaned it, changed all rubbers in the fuel system as well as cables and everything that was not close to perfect. I thought at the time that the throttle bodies looked great and had no visible wear.

Has anyone experienced issue like this? What could be the reason for it? How can this be fixed to make it possible to adjust the idle to lower RPM?

[roninvt]

Hi TIV,  my 1990 K75 idles a little under 1000.  Every once in a while it decides to idle at 1100.  But it drops back down after a day or two. 

[motodude]

My K75 had a similar problem.  It idled about 11-1200 RPM when warm.  I asked a (BMW) mechanic and his solution was to re-sync the throttle bodies to a lower RPM.  Basically, close off the idle by-pass screws a little bit and re-sync.  I'd prefer mine to idle about 8-900 RPM.

YMMV,
Tom

[TimTyler]

Do what Tom said.  I like mine at an even 1000.

[TIV]

Do what Tom said.  I like mine at an even 1000.

Can I sync it accurately with a Carbtune vacuum gauge or similar?

[TimTyler]

Carbtune is what I use.

Seen this thread?

And this one too.

[TIV]

Thanks a million Tim and others. This forum is a goldmine for me because there are very few K bikes where I live and a very little knowledge about the K´s. Your answers and these two links are what I was looking for. Next time I feel like wrenching a bit I´ll do it.

[jetpoweredmonkey]

I had the same problem and, again, what Tom said.  Your air bypass screws are open too far.  I had good results setting them all to about 1/2 turn from closed and re-syncing.  Unfortunately the service manual I have doesn't give a spec for the initial setting, but 1/2 turn seems fine.

[wmax351]

It can also be the throttle position switch (at the rear of the throttle bodies). It can hold the plates open. Make sure the stop screw touches the piece it sits on.

[Billk]

My 95K75 also idles at 1300 RPMs. I haven't been able to figure out why. I'd test it for vacuum leaks but did not find any. If it means anything, I can start my bike without the choke. If I ride it that way it will go off at the corner stop sign at which time I then use the choke to start it up again and keep it going till it warms up. I tested for vacuum leaks by using starter fluid. Next I will try using propane. The bike runs good and smooth with the exception of the top end. High speed over 5k RPMs is a little uncomfortable.