I have a backfire, not the Russian bomber but a loud detonation in the exhaust on over run, throttle off particularly after a period of high-speed riding, for instance on an exit slip after motorway riding. On my old K75 I would have immediately suspected the TPS and listened for the "click", but I understand that the Motronic uses a different sort of TPS with no audible indication that it is correctly adjusted. I have recently set up the throttle body bypass screws with a mercury manometer and easily obtained equal column heights. So, two questions: How do I check and adjust the TPS position? Is there any other likely cause of this behaviour? Thanks in advance.

With thanks to Drake Smith (Frankenduck) from the Motobrick forum
The TPS rational position can be adjusted by loosening the two bolts the hold it to the back of the throttle body assembly.

It should be positioned so that with the throttle closed and the bike turned on (but not running) you should get a reading of 0.375V between pins 1 and 4 of the TPS connector. Snap the throttle once or twice to make sure the throttle is fully closed.

FYI: It needs to be plugged in for this test. Just slip some thin wires into the connector when you connect it to monitor the voltage.

Thanks, Rick, I'll try that. Looking more closely there is blue paint undisturbed on the TPS screws, so it looks likely that the position has never been changed in 60000 miles.

Don't touch it, it is to do with the ballance between the butterflys and if you disturb you need some very expensive equipment to fix it. Like a flow bench.

Thanks for the warning, Rick. I don't mean the butterfly adjusters, I know not to touch those, but the two TPS mounting screws on the back end of the throttle shaft have the same paint on them. I assume that this must be disturbed to carry out the procedure described above.

I wouldn't worry too much about disturbing those but check the setting first. I f it hasn't been touched since new I would be very loathe to touch as they don't move with wear but could get dirty on the contacts. Can't help any futher on the contacts because I have never had one apart.

could still be the micro switch contacts mr grumpy ....(in the tps )

over time the spring action can change so affecting the affective range that the switch activates .....but does take a long time to happen ...a minor adjustment might help ...?

charlie99 wrote:could still be the micro switch contacts mr grumpy ....(in the tps )

over time the spring action can change so affecting the affective range that the switch activates .....but does take a long time to happen ...a minor adjustment might help ...?

Charlie it's a 16v and doesnt work the same as a 8v ones. It has 3 different reostats and gives 3 readings to the ECU which interprets that as the position of the throttle.
It doesn't have the idle or WOT switches.

thanks rick ...

but i thought there was a dead or off zone in the tps somewhere ....that i read in here and is like most modern tps devices in current production

found this ...which might help

http://k100rt.aforumfree.com/t938-k100rs-throttle-position-switch-info

read a good description by "kbike" for the setup proceedure ...post 19

I just got a GS-911 diagnostic tool for my S1000RR. There has been some discussion on the GS-911 site about whether that device could be used with a 16v K100RS through an appropriate adapter to the 3 pin connector under the seat. If so, perhaps some of these problems could be handled through the GS-911. Has anyone used the GS on a K100?

Thank you charlie99, and to KBike for the OP, I have done this today. I had no light at idle position and now, with a very small adjustment, I do. I will replicate the conditions under which the backfire occurs tomorrow, so hopefully it is fixed. One concern remains, the temperature warning light flickers uncertainly like a poor connection when it is lit in the throttle off position; is there any way of getting a shot of contact cleaner into the TPS without removing and dismantling it?