BMW K bikes (Bricks)

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1Back to top Go down    Stalling when hot on Thu Mar 02, 2017 10:18 pm

timz10000

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I think my '85 K100 had a couple overlapping problems. I seem to have fixed it stalling and not starting again by replacing the Hall Effect Sensors (also replaced air intakes and all fuel lines and and cleaned all electrical grounds).

Now however it still will run for about 15-30 minutes, then starts stalling and won't start. If I wait a few minutes it will start up again. It seems it's worse when I'm going slow, if I can get it up to 20 or 30 MPH it seems to be OK (that got me home). A couple times the oil and battery light lit when it stalled.

Things I haven't done
- no insulation under gas tank (will add)
- coolant is old but not disgusting (will replace)
- didn't replace vacuum hose
- engine breather hose doesn't go into air intake - previous owner blocked the entry to the air intake and the end of the hose rests on the engine

What should I consider troubleshooting next?

- ignition coils? (I haven't checked to see if they are the original kind that were bad)
- could a dirty radiator cause too much heat that would cause this? (Or would I see the heat warning light?)
- there's no plastic tray under the gas tank, and I understand there should be - would that make wires heat too much?

    

2Back to top Go down    Re: Stalling when hot on Thu Mar 02, 2017 11:08 pm

RicK G

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Oil and Alt light coming on is normal.
When you start it cold then let it warm up does it idle OK without the choke lever being opened.
To me it sounds like it could be air leaks in the intake system between the engine and air filter. As the Ks age they are very prone to these problems as the rubber components tend to get very hard and crack.


__________________________________________________
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
    

3Back to top Go down    Re: Stalling when hot on Thu Mar 02, 2017 11:17 pm

timz10000

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It needs the choke lever to start, but then runs nicely when cold

I just discovered i forgot to replace the front airbox clip - though it's still pretty tight with the filter (using a K&N filter the previous owner put on). Replacing the clip now.

I did replace all the rubber on the intakes so that shouldn't be leaking there

    

4Back to top Go down    Re: Stalling when hot on Fri Mar 03, 2017 12:02 am

Point-Seven-five

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When it quits, do you lose the spark on the plugs?  All four or just two?  As I understand it, the older K100 engines are known to have ignition coil failures.  I can't recall what the failure mode is for them, but there was a design change in the late 80's that is supposed to correct the problems the early ones had.  Perhaps someone with more knoowledge can suggest a test for them.

Normally, the only parts of an engine that stop working when they get hot are the electrical components in the ignition circuit.  You have replaced the weakest point which is the Hall Sensors which leaves the coils and the ignition module under the tank.  You might want to insulate the area between the engine and the tank.  the fact that moving helps means air flow under the tank is helping cool things.

I may be wrong, but I believe the new coils have dark orange terminals where the early ones were all black.  Again I am working from what I recall reading as I have no personal experience with the early coils.


__________________________________________________
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
    

5Back to top Go down    Re: Stalling when hot on Fri Mar 03, 2017 12:10 am

Laitch

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@timz10000 wrote:Things I haven't done
- engine breather hose doesn't go into air intake - previous owner blocked the entry to the air intake and the end of the hose rests on the engine
If you are referring to the part indicated by the red arrow in the attached illustration from the MAX BMW parts fiche, replace it and reconnect it. That may help.


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1995 K75T 60,000 miles
    

6Back to top Go down    Re: Stalling when hot on Fri Mar 03, 2017 12:46 am

RicK G

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The early coils were a very dark grey to black and were very prone to the secondary coil going open circuit which eventually led to total break down of the internal insulation between layers of the coil windings and little to no spark.
It was around the release of the 87 model that they were changed to the brown with orange towers on them, a much better coil and a straight replacement.


__________________________________________________
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
    

7Back to top Go down    Re: Stalling when hot on Fri Mar 03, 2017 1:51 am

charlie99

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I wonder have you looked at valve - shim clearances ...

if too tight could well be an issue ...I have a memory that the exhaust valve clearances do regress over time ...and worth testing = measuring before you do ANYTHING else

it isnt hard ...but needs to be done before any symptoms  could be diagnosed ..I guess your looking for 10 -12 thou clearances cold

some one will correct me if I got the clearances wrong ...but 6-8 thou is likely too tight

good luck


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cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

8Back to top Go down    Re: Stalling when hot on Fri Mar 03, 2017 8:53 am

Holister

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Mine were way tight a while back on the old girl and she was stalling at the most inopportune times. However, she would start back up straight away. As you say, worth checking asap as too tight can lead to burnt valves and I would be checking those just to be sure.

A guy I know up the coast struggled with the exact same problem described above for a long time. 20 mins down the road the engine would stall. I suggested it could be the temp sensor. He checked it and sure enough it failed at operating temp. He bought a new one and after he installed it.... same problem!! I couldn't convince him that the new one might be dud as well but after a few days he put the meter on it and sure enough it was failing at operating temp.... go figure. Anyway he ordered another temp sensor and this time problem fixed.
DMM on FICU pins #10 and #13 (count from the lead end) should read 2.5kΩ at 20ºc and below 300Ω at operating temp. Detailed instructions are listed on the Trouble Shooting page off the Portal tab.


__________________________________________________
1988 K100RT     VIN No.  0094680
1989 K100RT     VIN No.  0097367 (naked)  
1996 K1100RS   VIN No.  0451808
     Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

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