BMW K bikes (Bricks)


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blacksmith adam

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The bike started as normal, rode down the drive just going through the gate and the bike cuts out, grrrrrr!!!!! . Press the button, it fires for half a second and cuts out again.
I manage to get it ticking over (just) but the engine is cold and as soon as I put the choke on it cuts out, as soon as I turn the throttle it cuts out. The engine will only turn over when the throttle is open and will not fire until the throttle is closed. BIG Grrrrrr. Embarassed
So I’m assuming the throttle position sensor is broke.
Has any one had experience of this problem?
Is there a way of testing the TPS? Or am I on the wrong track.
Any ideas would be appreciated!  

    

Point-Seven-five

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Have you been riding it before today?  Just done some work on it?  If so, what did you do?  Can you hear the fuel pump run?  How are the rubber bits?

What model?  What year?


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Present:
1994 K75RT
1994 K75S
1992 K100RS

Past:
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

92KK 84WW Olaf

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Using choke and opening throttle is the same thing, the 'choke' is just a means of getting some throttle opening. So opening throttle and opening choke will both have the same effect.

On some models [as far as I know its the 8 valve engines] we disconnect the TPS altogether when it goes wrong. 

You seem to be saying you can start it and get a tickover. That implies fuel is flowing both at start and at run mode.

If yours is the K with the bolted down petrol tank the front left of the tank has the electrical connection to the fuel pump. It can get loose and produce a bad electrical connection effectively restricting or cutting off the fuel supply. If its loose open up the pins a little to make them a tighter fit. You will have taken this off when you removed the tank.

Another place I have come across a problem like this was the control unit under the seat having a badly connected plug. There is a little grub screw in this, make sure the connection is correct and the screw is in place. I imagine you have had this out so its a risk area.

That's two easy checks to start with.


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1992 K100LT 0193214 101,000 miles
1984 K100RT 0022575 Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 58,645 now 60,500 miles
    

blacksmith adam

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Thanks Olaf ill give those ideas a go

Thanks Point-seven-five, Its a K100rs 1986 I just changed the shims and balanced the TB then rode 130 miles in one hit with no problems, it ran a lot smoother, most of the rubber bits are new ish. I can hear the fuel pump and I don’t think it a lack of fuel problem.

    

Point-Seven-five

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Ok, just to clarify, the engine starts and runs with the throttle closed.  Dies when the throttle is opened.  Is that correct?


__________________________________________________
Present:
1994 K75RT
1994 K75S
1992 K100RS

Past:
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

blacksmith adam

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@Point-Seven-five wrote:Ok, just to clarify, the engine starts and runs with the throttle closed.  Dies when the throttle is opened.  Is that correct?
yes, it runs with the throttle closed, but struggles which i think its down to being cold

    

Point-Seven-five

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It sounds like the mixture is running lean.  Opening the throttle either with the grip or the "choke" adds enough air to the mix to kill the engine. 

Outside of the Engine Control Unit(ECU), the problem is possibly the result of several things.  First, poor fuel delivery, either because of a failing fuel pump or a plugged fuel filter.  It may also be that the fuel pressure regulator is not keeping the pressure in the rail high enough. 

Second, engine temperature when cold is sensed and commands the ECU to enrich the mixture.  Could be a sensor failure or a bad electrical connection.

Last, there may be a vacuum leak that is allowing more air into the idle mix making it sensitive to additional air at the transition point to partial throttle.  Double check all the vacuum caps on the throttle bodies and all the vacuum hoses running around the engine.  You won't be the first one to leave a vacuum cap or hose off after doing a throttle body balance job.


__________________________________________________
Present:
1994 K75RT
1994 K75S
1992 K100RS

Past:
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

blacksmith adam

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Thanks i'll work through those ideas

    

Dai

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You can always pay my ferry fair...? No? Sad


Oh well. You can always phone me instead. Very Happy


__________________________________________________
'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

blacksmith adam

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@Dai wrote:You can always pay my ferry fair...? No? Sad


Oh well. You can always phone me instead. Very Happy
i'll ring mid morning, did'nt know what time you were working till

    

Dai

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Work is always 15.30-00.00, so I'm usually available between 10.00-14.30.


__________________________________________________
'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

RicK G

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Make sure the fuel pump is actually running when the engine is running and not just when the starter button is pushed.  They will idle for quite some time on the residual pressure after the pump stops.


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If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

Dai

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Fixed it Rick. A good shove on the FICU plug worked wonders apparently.


__________________________________________________
'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

92KK 84WW Olaf

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@Dai wrote:Fixed it Rick. A good shove on the FICU plug worked wonders apparently.

Was that the same as on post 3?


__________________________________________________
1992 K100LT 0193214 101,000 miles
1984 K100RT 0022575 Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 58,645 now 60,500 miles
    

Dai

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You got it Olaf. Adam followed your instructions.


__________________________________________________
'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

blacksmith adam

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BIG Thanks to all! Problem fixed,
It was the control unit, after giving the connection a push and nothing changing, and going through everything else I gave it a frustrated wiggle and It worked. I cleaned the connections, there was a strange varnish like muck on it, put some electrical silicone grease on and it now works a treat!  
Time to ride some more happy miles

    

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