Engine won't start unless i keep holding the starter button and gas it

[noppo]

Hiya.

I need help with my 92 K1.  Any takers?  i'm having issues with it not staying running until i keep on the gas and get past the sweet spot.  When cold, it will start and run for 1/2 a second, and then stop.  i keep starting it while i finagle the throttle and the starter to make it run, and once i get the revs up, it will stay running.  It only does this when the motor is cold.  As i know them to be, the facts are:

* 52,000 Kms (not sure about miles anymore)
* Choke on full (until the 1st detent)
* Bike is on level ground,
* On the center stand; side stand up
* 1/4 tank full,
* fuel pump seems to be in good working order (i turn the key on, i can hear it for 1 or 2 seconds and then it stops) which seems to be the norm for this bike
* Recently replaced brake light bulb (today)
* Recently reset ABS (1 month ago)
* Battery charged and in good order
* The last bike trip was during incessant rain
* Regular unleaded gas (to date there have been no issues with the gas i run)

If anyone can share some advise, i'd appreciate it. Typically this is a zero issue bike except for when the battery gets low on occasion.  Other than that, it's a righteous scoot.  Welcome your thoughts.

[Laitch]

* Choke on full (until the 1st detent)

What happens if the first time you start it you put the choke on the 2nd detent and don't touch the throttle? Have you checked the spark plugs to see if they are wet or dry when the bike fails to start? Are the spark plug gaps within specification?

[K1300S]

when was the last time it was tuned up?
plugs
valves
TB synch
fast idle adjust
TPS adjust
mixture adjust

those are the first things to check.  all of them.

[rbm]

So you say it's hard to start from cold, and you have to keep on the gas until she warms up.  Then after she warms up, she's good to go.  Does that sound like what you're experiencing? 


If so, I'd bet 95% it's the water Temp sensor in the stand pipe.  You could so some diagnosis first if you want.  First check that the connection is clean and solid to the harness.  If corrosion around the threaded part of the sensor, it might be worthwhile to drain the coolant and clean the threads.  While the sensor is out, check its function to make sure it is the correct values at the correct temperatures.


But, if you want to avoid all this fiddling, then just change the sensor.  BMW P/N 13622242184

[noppo]

If so, I'd bet 95% it's the water Temp sensor in the stand pipe.

Correct. It's an iterative process with gas and starter and gas and starter again, and on and on (sometimes both at the same time) until the engine stays running and gets to the sweet spot in RPMs.  Then i can cut the motor and i'll start right up.  It's an ugly process actually. Anyway, you got it right.  Sorry - what's a stand pipe?

One more fact -> the temp gage and light are not working.  i thought it would have absolutely nothing to do with the starting problem, but maybe i was wrong.  It worked when i parked it.  :musicboohoo: So, i just now pulled the temp gage, and saw that the wires leading to the temp gage harness were not connected to anything. :yow  They seem to have been melted by engine heat caused by the radiator fan failure 2 years ago. The temp gage unit wires look fine. Maybe the above adds some color to all of this?

So, i have some more homework to do now.  i'll check the sensor and go from there.  Gotta find that sensor.

[rbm]

Item #13 in the diagram.



Picture of the sensor, with the harness disconnected.





Your temperature gauge is not connected in any way with your starting problem. The temperature sensor for the gauge is located in the water pump.


The temperature sensor I show above is responsible for telling the ECU the temperature of the engine and for turning on the cooling fan.  It's interesting that you mention the overheat light because it is associated with the above sensor and drives the temperature module in the relay box.  If the above temperature sensor is bad, it will upset the light and the ability of the Motronic to manage the fueling to the engine.


To get the gauge working trace the wire from the gauge down through the Hall sensor cover, through the water pump and to the temp sensor on the left side.  It is possible the connection to the sensor is bad and needs some attention.

[Inge K.]

It's interesting that you mention the overheat light because it is associated with the above sensor and drives the temperature module in the relay box. 

The temperature module isn't present on the 4V models. The signal from the temp sensor goes to the
Motronic unit, which manages the fan and the overtemp warning light.

[noppo]

Thanks guys.  i will have to get to this on Sunday. Won't have time until then. Thanks for the comments. Very helpful. So, "stand pipe" = vertical pipe. Captain obvious here!  Yea mine is a k1 so it's got 4 valves per cylinder.

[rbm]

The temperature module isn't present on the 4V models. The signal from the temp sensor goes to the
Motronic unit, which manages the fan and the overtemp warning light.

Thanks for the clarification, Inge.  Goes to illustrate my lack of experience with 4V models.