BMW K bikes (Bricks)

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1Back to top Go down   rough running 16v K100  tps Empty rough running 16v K100 tps Wed Mar 24, 2021 11:43 am

warmshed

warmshed
active member
active member
I am looking for the cause of rough running and the bike wont rev over 6k rpm in any gear. will only run correctly on the road at gentle throttle opening, bogging down when asked for more.

Tried to set the TPS but could only get the voltage to go down to 540mV, Using an AVO digital meter with ignition on but engine not running. Tried "snapping" the throttle to stabilise the TPS but could not get it lower than 540mV. No more movement on the adjusting slots. So what am I doing wrong? or is the TPS stuffed. The engine starts easily and tick-over is good.

Tried so far:- New pump and filter. Plugs, coils, checked fuel and vacuum hoses. compression good and all pots the same. Tested fuel pressure, seemed a little low but may be due to the Chinese gauges. Cleaned injectors (though no evidence of dirt) Help please

    

2Back to top Go down   rough running 16v K100  tps Empty Re: rough running 16v K100 tps Wed Mar 24, 2021 2:22 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
There is a built in diagnostic for setting the throttle position sensor (TPS).  Follow the instruction in the link below. You don't need an LED, the temperature idiot light comes on at idle and goes out just as the throttle is opened.

https://www.kforum-tech.com/electrical/PDF/Motronic%20Fault%20Codes.pdf


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

3Back to top Go down   rough running 16v K100  tps Empty Re: rough running 16v K100 tps Fri Mar 26, 2021 7:44 am

warmshed

warmshed
active member
active member
Have a diagnostic tester and done all tests. Cannot get the TPS to light the led no matter how far I turn it, tried setting it on a multimeter, which is more accurate but can only get it down to 540mv rather than 370mV as mentioned. Bike only done 18k miles so would not expect the tps to be worn which is why I was asking if there is somethine I have done wrong. Would also like to know what effect a high reading would have on the running? Thank you

    

4Back to top Go down   rough running 16v K100  tps Empty Re: rough running 16v K100 tps Fri Mar 26, 2021 11:13 am

Point-Seven-five

Point-Seven-five
Life time member
Life time member
The amount of air entering the engine is inferred by the Motronic ECU from throttle position, and then the amount of fuel injected is calculated from it. Because of that, having the correct starting point is critical to having a proper air/fuel mixture throughout the entire engine operating range.

Do you have Deoxit contact cleaner? Clean the TPS terminals. Also, check the wiring for continuity between the TPS and the terminals on the big connector on the Motronic brain.

The TPS is a potentiometer. Can you get reading of the resistance between the terminals? I think there is some data on what you should see in the troubleshooting guide on this site.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

5Back to top Go down   rough running 16v K100  tps Empty Re: rough running 16v K100 tps Fri Mar 26, 2021 12:53 pm

Laitch

Laitch
Life time member
Life time member
@warmshed wrote:Cannot get the TPS to light the led no matter how far I turn it . . .
Did you adjust the CO value when you balanced the throttle bodies and set the idle? With the LED disconnected and not being a distraction, can you get the overheat light in the instrument cluster to light when you rotate the TPS?

In the preface to the instructions you are following, the author indicates values were developed using a K1100 and that they "may" be valid for other models; the implication is that they aren't necessarily valid for other models.

If the engine idles and accelerates smoothly and its CO value is correct, I wouldn't get hung up on the MV values. I'd be riding if I could, but there are seven miles of mud ruts and potholes on the gravel road between me and pavement for the next few weeks so there's that.


__________________________________________________
1995 K75 81,000 miles
rough running 16v K100  tps Usa-lo10
    

6Back to top Go down   rough running 16v K100  tps Empty Re: rough running 16v K100 tps Fri Apr 09, 2021 5:23 am

warmshed

warmshed
active member
active member
Well, finally got my bike to run well. I cleaned and changed the filters and O rings of thech injector. They all looked spotless sso was the fuel rail. Gave them a good back flush with IPA. Each one gave a good long squirt when flushing it the correct way.  

 The bike now runs smoothly and power is back.   Still  looking into the TPS issue. 
 Many thanks for your replies.

    

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