BMW K bikes (Bricks)

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Rockman


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My RT just cut out today, about 10km from home. I did notice that the starter motor was sluggish, so I thought maybe the battery was stuffed, but everything else looked ok. I started coasting it down hill and out of interest, stuck it in second gear and it jump started no problem, so I continued on for a km or so, did what I was going to do but left the bike idling, and then headed back towards home. It got to the top of the same hill, then stopped again. A nice young lady from a nearby farmhouse let me park in her yard off the road and gave me a lift into town as well.

The fuel pump is running ok, the starter motor is sluggish sometimes, but not others, lights etc all seem to be working ok. When it is going it runs well.

I'll strip and clean the ignition switch over the weekend, but really to me it seems like a relay is on its way out or a connector or something.

Apart from the ignition switch, any other suggestions?

    

RicK G

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Check the starter brushes they can make it slugish on turnover.  Hall sensors could be the problem but I wouldn't be going there just yet.


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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
    

Garyk100

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Just a thought but mine used to cutout then run for while and cut out, turned out to be the fuel filter I think it was the original had never been changed, maybe not connected to your troubles but worth considering, Gary


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The early bird catches the worm, but the second mouse gets the cheese

1991 K100rs16v
1993 K1100LT
    

Rockman


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Yesterday arvo I went out to pick it up with my ute. Of course it started up straight away, so I decided to try and ride it back to town. It went about 5km before cutting out again, this time at the start of a long downhill section so I was able to coast another km or so. Put it in gear and it started again so I rode another 2-3 km when it cut out again, about 300 metres from home, but at the bottom of a steepish hill. By then I had sussed that it was temperature related, and if I let it cool down it would go. So I ran the mate who was driving my ute home and drove back to the bike. It started straight away so I rode it home and walked back for the ute.

So what is the outcome of all this saga? It is temperature related. I suspect some sort of problem with the temperature sensor tripping early and cutting the ignition off. I did notice that the temp gauge has stopped working but that may be a separate issue. It is definitely not overheating.

As for the starter motor, its not long had new brushes (5000 km?) so it should be ok, but I'll get as set of brushes for my spare starter motor just in case. HE sensors Rick? do they go out with heat and come back when it cools down?

I dont think it is the fuel filter, but I have a new one so I'll fit it anyway.

    

duck

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If it dies when it heats up and then runs again when it cools down then that is a classic symptom of a dying Hall Effect sensor.

Other usual suspects for intermittent electrical death are the ignition switch and the fuel tank connector.


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S
14 Yamaha WR250R
http://www.ClassicKBikes.com
    

Rockman


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duck wrote:If it dies when it heats up and then runs again when it cools down then that is a classic symptom of a dying Hall Effect sensor.

Other usual suspects for intermittent electrical death are the ignition switch and the fuel tank connector.
Is there any way to test the HE sensors in the dying stage?

I have a test unit I made up for a R1150GS a few years ago but that is a yay or nay thing so I'd have to wait until it has cut out to try it.

As for the ignition switch and fuel tank connector, these wouldnt necessarily be heat related. This seems consistent, when its cooled down it goes, warm it up, it stops.

    

kennybob

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Engine Running:
Maybe get a hot air blower gun such as used for electrical heat shrink, or a 100W hair dryer, and aim the heat at the sensors to see if you can get it to fail early before the engine warms up. 

Then blow compressed air or run a fan to cool the sensors quickly to see it if starts back.

If you can do the preheat before the engine heats up then it might rule out other heat factors and isolate it to the HES.

Engine Off:
Maybe you can use your test equipment to monitor the HES signal with the engine off and use the heat gun to get it hot enough to trip out, then cool it with fan or compressed air and the test signal returns.

    

duck

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Aside from the heat gun thing, one thing I've heard of is carrying a bottle of water with you. When the bike heats up and quits, pull over and douse the cover plate to cool the HES down and then see if it runs again.


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S
14 Yamaha WR250R
http://www.ClassicKBikes.com
    

9Back to top Go down    Place to look on Sat Jul 30, 2016 8:15 am

buddymack

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I had a similar series of mystery cutouts, which ultimately proved to be the Starter Brushes.  One side of the Starter Brushes is used as an additional ground when the engine is running above 710 rpm.  I would also make sure the ground wire to the right hand switch is clean, tight and functional.   

Along the way though, I discovered my green starter button was involved.  Is your green button completely intact?  The button is made like a pencil eraser with a mushroom cap top.  The flexible mushroom cap is the only thing that pops the shaft of the button back into position and off the internal contacts once you've started the engine.  When the top mushroom cap portion of the green button finally dries out and pops off leaving only a green "eraser stub" shaft in the hole, it still works, but now there isn't anything to pull the remaining "eraser stub" portion up and off of the switch's internal contacts.  That allows that "stub" float in and out and momentarily contact the metal tabs in the switch, and each contact tries to activate the starter.  The bike is designed not to allow the starter to engage if the engine is spinning at more than 710 rpm, so you never hear the starter, but the Shed Relay is engaged by those contacts and it then kills all power to everything but the Starter ("sheds" all other electrical loads to route all power to the Starter).  With the engine running above 710 rpm, the bike then uses one side of the Starter brushes as an additional ground.  Clever huh?  

Anyway, I think that is a fairly accurate description of my issues.  A new right hand switch and starter brushes eliminated the cutouts.  Good luck.

    

olfart47

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Rockman wrote:Yesterday arvo I went out to pick it up with my ute. Of course it started up straight away, so I decided to try and ride it back to town. It went about 5km before cutting out again, this time at the start of a long downhill section so I was able to coast another km or so. Put it in gear and it started again so I rode another 2-3 km when it cut out again, about 300 metres from home, but at the bottom of a steepish hill. By then I had sussed that it was temperature related, and if I let it cool down it would go. So I ran the mate who was driving my ute home and drove back to the bike. It started straight away so I rode it home and walked back for the ute.

So what is the outcome of all this saga? It is temperature related. I suspect some sort of problem with the temperature sensor tripping early and cutting the ignition off. I did notice that the temp gauge has stopped working but that may be a separate issue. It is definitely not overheating.

As for the starter motor, its not long had new brushes (5000 km?) so it should be ok, but I'll get as set of brushes for my spare starter motor just in case. HE sensors Rick? do they go out with heat and come back when it cools down?

I dont think it is the fuel filter, but I have a new one so I'll fit it anyway.
had this going on with my r1100rs turned out there are TWO relays for fuel one small and one large it turned out to be the BIG one changed out both and never cut out again I would try this before changing out the hall efs a lot cheaper which I found out the dear way

    

Crazy Frog

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Rockman wrote:So what is the outcome of all this saga? It is temperature related. I suspect some sort of problem with the temperature sensor tripping early and cutting the ignition off.
When in an overheating state or having a bad temperature sensor, a K bike will NEVER cut off on its own. However if the bike temperature is over the maximum allowed, it will not start.
Your obvious problem is the Hall sensor and the only test available is the heat gun. (unless you want to put them in the kitchen oven and having your wife chasing you with the rolling pin ).


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1986 k75, 1985 K100rt, 1985 K100rt/EML sidecar.
    

RicK G

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Phil I have several HES plates I can post one Tomorrow (monday) if you want. I would recommend that you only do a temp fix with it and put new sensors on the old plate when you get some.


__________________________________________________
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
    

Rockman


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RicK G wrote:Phil I have several HES plates I can post one Tomorrow (monday) if you want. I would recommend that you only do a temp fix with it and put new sensors on the old plate when you get some.
Thanks Rick. I'll borrow one and try it if thats ok. PM'd you my postal address.
If it fixes the problem then at least I know what it is.

I do have a couple of new sensors I got off Captn H a while back, but this would mean removing the old ones from the mounting plate and I wouldnt do that unless I was sure it was the problem.

As for the starter motor, I'm almost sure the battery is on the way out so I'll replace that before going any further. It was in the bike when I got it, and that was 3-4 years ago.

    

jumpinjimmy

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I'm having this same issue at the moment and I changed the hall sensor on the recommendation of the forum and that wasn't the problem.  Just so you know.

    

Rockman


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jumpinjimmy wrote:I'm having this same issue at the moment and I changed the hall sensor on the recommendation of the forum and that wasn't the problem.  Just so you know.

Did you find out what the problem was?

    

jumpinjimmy

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In my case, I changed the filter, fuel pump, HE sensor, jiggled wires with no results.  A couple of days ago I was looking in the gas tank and moved the fuel filter position because the the gas line looked like the bend back to the filter was too extreme, although not kinked.  Ever since then, the bike is running great.  I'm puzzled.

    

Garyk100

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Garyk100 wrote:Just a thought but mine used to cutout then run for while and cut out, turned out to be the fuel filter I think it was the original had never been changed, maybe not connected to your troubles but worth considering, Gary
When my fuel filter was let's say not functioning properly, the bike would run but occasionally act like it ran out of petrol, even backfired once or twice, I replaced leads and plugs thinking it was electrical, then a mate asked if I had changed the filter, changed the filter never had a problem since, just a thought


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The early bird catches the worm, but the second mouse gets the cheese

1991 K100rs16v
1993 K1100LT
    

Roland5

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Greetings all.  I had a similar issue that appeared to be a hall sensor.  The bike would die in nearly the same place on the way to work.  A slight frustrating delay and the bike would start and run only to die at another completely random distance/temperature/load/speed.  It was a very frustrating intermittent gremlin.  I replaced the sensor (without testing) and it was not the problem.  It finally boiled down to the fuel injectors.  I checked the connections at the FIs and they appeared good.  I then traced the wire back to the under tank connector which APPEARED to be good.  However, the plastic of the connector had become brittle and cracked.  The crack was allowing the connector to separate slightly which would cut the power to the FIs causing instant(ish) death.  (There was always some sputtering and then death ... but death nonetheless.)  You may want to check this connection and ensure that it is well made and doesn't just appear to be well made.  I will hope this is your issue.

good luck
Roland 

ps... I just ran into this connector issue again during my latest refurb, replacing fuel lines.  I must have jiggled the connector and, again, it appeared in tact.  I was wrong ... I made a more thorough repair and it fired right up... I love these bikes.


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Roland Antumblen
85K100RT - BlacK Beem
Toad Suck, AR
    

Rockman


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I havent got to mine yet, but my money is still on the HE sensor. Its very consistent. It'll run well until it has warmed up, then just cut out instantly. Let it cool down a bit and it will run again. There is nothing to suggest fuel filter problems, pinched hoses or otherwise. I now have another HE sensor plate to try (thanks Rick) but it will be over the weekend.

    

jumpinjimmy

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Rockman, I hope the hall sensor fixes your problem...as for me, since I've changed mine already and it didn't help, I'm going to check the connector under the tank.  Sounds like a reasonable explanation and probably would be worthwhile looking into that, too. 

Keep us posted!!

btw, I bought the hall sensor kit that's on ebay (from Germany for 125€) and it was a very easy fit.  Only two issues were fitting the connector over the engine (remove the radiator shroud) and then passing it through the grommet in the tray under the tank.  Nothing too difficult.

    

92KK 84WW Olaf

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I was wondering does the failing HES cause the K to die within 5km? It seems a very short distance but maybe hotter climate than we have here.


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1992 K100LT 0193214 101,000 miles
1984 K100RT 0022575 Baja Red bought 36,000 now 87,100 miles
1997 K1100LT 58,000 miles
    

Holister

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I was wondering the same thing Olaf. I've not experienced HES problems but from what I gather they need to get fairly hot before they fail.
5km and i'm only just getting to operating temp.


__________________________________________________
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
    

RicK G

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The HES is inclusive in the engine and aluminium conducts heat very quickly, so if the engine is up to operating temperature then the HES is as hot as it going to get. That would take at the most about 2 miles of riding, the thermostat makes sure it happens.
One thing I saw further back in the thread was about the engine cutting out completly. This will only happen if the 2-3 sensor is the faulty one because the ECU takes its signal to energise the injectors from that and if it fails thee injection stops but not so for 1-4 sensor, that just stops 1-4 coil from working. So it can keep running on 2 cylinders if the 1-4 sensor fails.


__________________________________________________
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
    

Rockman


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RicK G wrote:The HES is inclusive in the engine and aluminium conducts heat very quickly, so if the engine is up to operating temperature then the HES is as hot as it going to get. That would take at the most about 2 miles of riding, the thermostat makes sure it happens.
One thing I saw further back in the thread was about the engine cutting out completly. This will only happen if the 2-3 sensor is the faulty one because the ECU takes its signal to energise the injectors from that and if it fails thee injection stops but not so for 1-4 sensor, that just stops 1-4 coil from working. So it can keep running on 2 cylinders if the 1-4 sensor fails.

In my case, it seems to stop at the top of hills. Maybe going uphill warms it up just a little bit more. If I can get over the summit and coast down the other side it'll start again after cooling down just a little, and then runs until the next uphill.. Sounds like the 2-3 sensor as it stops instantly. I'll swap the plate over saturday arvo and find out.

    

ainsjac

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Well in my case I should have no problems. Many have said that I am well and truly over the hill.


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AINSJAC
1983 K100 basic vin 0003960 colour red
1987 K100RT vin 0094685 colour, orange peel, sorry, pearl
    

Holister

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Maybe your thermostat is not opening fully, so it heats up quickly.... combined with dud HES.
Just a thought


__________________________________________________
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
    

Dinosaur

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Had the same intermittent engine cut out problem on a K75. 

Went down the replacement HES route without fixing it. Long story cut short is that the fuel pump was shutting down due to voltage drop. 

Once the fuel pressure drops the engine ECU decides no spark is needed. Cause of voltage drop was a cracked solder joint on the internal terminal post for the fuel pump wiring. It expanded as engine heat was absorbed by the mounting plate on the bottom of the fuel tank. 

This explained why the bike went further on colder days and often cut out at the top of a hill when engine heat had increased. 

Fault was found by checking voltage across all connections at the time of cut out. No point checking after it cooled down because the crack had closed and all voltage readings were normal.  Crack was only noticed after looking very closely with a magnifier.

BTW the fuel pump operating voltage threshold appears to be about 7.3 volts. Any lower and it doesn't want to play.

Have not had a recurrence since resoldering the terminal. 

Crack may have been result of age and vibration.


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;BMW; 1985 K-100RS #0084201
    

Rockman


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OK, got it sorted over the weekend. 3 4 things fixed.

I replaced the HE sensor plate. It goes well now without any cutting out etc, so that fixed that.
Interestingly, one of the sensors has come apart, with the metal bit loose in the plastic holder and it was touching the drum. Bit odd I thought.

Ive had the battery on charge for a week and it seems to have come up ok. No hint of starter motor problems.

I fixed the connector that goes to the fuel pump, which has been dodgy for a while. I got a big pair of pliers and gently crushed the female side of the connector so that they were oval, giving me a good connection. I should replace the whole connector at some stage.

And I fixed the temperature gauge. The wire had just dropped off the sender on the water pump.

So I'm a happy chappy.

    

ainsjac

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It does feel good when a number of things are sorted out. Well done.


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AINSJAC
1983 K100 basic vin 0003960 colour red
1987 K100RT vin 0094685 colour, orange peel, sorry, pearl
    

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