Hi,

After refueling this morning, to bike suddenly had a idel speed of 2000RPM, instead of the normal 1000RPM.

I had driven about 12km, stopped for gas, and then when I started again it had changed.

The bike rides just normal, no lack, but after a hour on the motorway it had 2 misfires in the exhaust, when  deaccelerating of the motorway.

Any ideas, what to check?

Check that the throttle cable is not holding the throttle open a tiny amount. If the throttle is open a tiny bit the throttle position sensor wont shut the fuel off when you decelerate and fuel can get into the exhaust and burn there.
Where the cable exits the RHS switch block there is a small cone shaped rubber boot if you pull that back onto the cable you will see a small adjuster. There should be about 1-2mm of slack

Afterfiring on the K75 during deceleration is more prevalent than on the K100 and causes may be linked to:

1) check the throttle position switch on the rear of the throttle bodies is working - when the throttle is close you should have continuity on one set of the contacts .. this cuts the fuel supply to the motor if the revs are over 2,000 rpm. The throttle switch position is adjustable. Also, I've noticed a mistake I make when I adjust the switch. I sometimes apply a little downward pressure to the switch as I tighten the screws; this is bad because it causes binding.  Make sure to keep the switch centered on the butterfly shaft.

2) there is an air by pass that adjusts the fuel mixture at low air speeds .. under the fuel tank inside the air cleaner bits.. but check number 1 above first. This is normally set with a CO2 meter..

3) Another thing that can cause the afterfiring on deceleration is a leak anywhere in the leading 40cm (or so) of the exhaust system. The gasket between the exhaust header and muffler connection can deteriorate and cause air leakage.  I recommend Permatex Ultra-Copper high temp RTV silicone gasket maker #101BR for the aftermarket slip-on system joints. Good to 700˚F intermittent. Available in auto parts stores.

4) Could be the fuel pressure regulator, measure fuel pressure...should be 2,5 bar.  Next, check the water temp sensor.... measure the resistance between contact 10 and 13 at the FI ECU connector. You should measure ~2,5 Kohm at 20 degree Celsius.

Thanks for all your help.

I started checking the "choke" and speeder cable, but count find anything wrong, but after the check all was fine, so I recon the cables need some lubrication, so that is my next project.

Cheers

Peter

The original cables is teflon lined and should not be lubed according to BMW.

Oh. Good that I didn't start yet.

So I just hope the massage helped.

Thanks Inge.

If the cable has been oiled it could have picked up a lot of dirt/dust which will make it stick so cleaning it can help.
If you feel it does need some lube the silicone in a spray can is good as it wont collect dust.