BMW K bikes (Bricks)


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PhillipRambo

PhillipRambo
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Hello

I have a BMW K75C as my daily bike, and today i experienced that my bike died while standing still and ideling. Afterwards i tried starting it in neautral and with the cluthc in afterwards and it wouldnt start! It crancks over perfectly and it seems that i can hear my fuel pump running. I then had to park it and take a cap to work. After i got home i tried starting it again, and now it started first try without any problems! What could be the issue? and how should i go about finding it. When the bike runs, it runs perfectly and i have no problems what so ever, all of sudden it just cuts out and cant be started for a couple of minuttes/hours.

    

Suzi Q

Suzi Q
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There'a an almost endless list of fairly straightforward checks:

I'll start you off (let's try and do this is order of easiness): when it next happens, try opening the fuel cap - a blocked vent could cause fuel starvation.


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Sometimes I'm not really Suzi Quatro.
    

PhillipRambo

PhillipRambo
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Suzi Q wrote:There'a an almost endless list of fairly straightforward checks:

I'll start you off (let's try and do this is order of easiness): when it next happens, try opening the fuel cap - a blocked vent could cause fuel starvation.
Yes, i tried that, but it didnt help. Didnt thinks it would be a problem since it usually starts

    

Laitch

Laitch
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Next easiest to check is the fuel filter. Remove it then blow through it in the direction of fuel flow. If your cheeks look like those in the image below, it is probably clogged and should be replaced.
BMW K75 dies out sometimes and wont start for a while Scree279

    

redrockmania

redrockmania
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Laitch re your Post 4. What's the BMW part number for the little critter who clears blocked full filters? How about a group buy!

    

PhillipRambo

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Good idea, i will check the fuel filter. What about the hall sensor, couldnt that cause problems, or can i rule out the ignition system?

    

Laitch

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PhillipRambo wrote:Good idea, i will check the fuel filter. What about the hall sensor, couldnt that cause problems, or can i rule out the ignition system?
Bad juju, ancestral curses and corroded ignition switch contacts could also be suspects.  Smile  It's best to focus on one thing at at time.

    

Suzi Q

Suzi Q
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Very generally,
Ignition faults cause an engine to cut out - running fine one minute and then completely dead the next. The exception is a spark plug or HT lead fault which causes misfiring or general poor running.
Fuel faults cause a reluctance to rev, or a weak-feeling engine, or dying out and then re-starting after a few minutes seemingly okay. The exception is an injector fault, which causes misfiring or general poor running, and possibly a reluctance to start.
That's only a rough guide though and, I guess, frustratingly unhelpful.


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Sometimes I'm not really Suzi Quatro.
    

Laitch

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Suzi Q wrote:That's only a rough guide though and, I guess, frustratingly unhelpful.
Cheer up, Suzi! It could cause an argument. cheers

    

PhillipRambo

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Suzi Q wrote:Very generally,
Ignition faults cause an engine to cut out - running fine one minute and then completely dead the next. The exception is a spark plug or HT lead fault which causes misfiring or general poor running.
Fuel faults cause a reluctance to rev, or a weak-feeling engine, or dying out and then re-starting after a few minutes seemingly okay. The exception is an injector fault, which causes misfiring or general poor running, and possibly a reluctance to start.
That's only a rough guide though and, I guess, frustratingly unhelpful.
Okay, thanks, i guess i might have to go through it one thing at a time.I will start by going through my wires and making sure there is good ground and generel connection. This is going to take a lot of time Rolling Eyes

    

92KK 84WW Olaf

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Hall sensor?


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 49,200 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 63,390 miles

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

12Back to top Go down   BMW K75 dies out sometimes and wont start for a while Empty Dies sometimes Thu Oct 12 2023, 18:01

daveyson

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Is there a pattern, like the tank is always full when it happens. How long was it idling before it conked out, is the time span a pattern?


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

PhillipRambo

PhillipRambo
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92KK 84WW Olaf wrote:Hall sensor?
Yes the hall effect sensor, is a part of the timing of the ignitionsystem if im not mistaken Very Happy

    

PhillipRambo

PhillipRambo
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daveyson wrote:Is there a pattern, like the tank is always full when it happens. How long was it idling before it conked out, is the time span a pattern?
Today i took it for a spin to see if there was a sort of pattern. It started up as usually does, and after i had been driving around the neighborhood for about 7 minuttes it then shut down. Its a immediate shutdown.. . It's just like someone flipped a switch, and the engine goes silent. This has been consistent each time it's happened.

Given this behavior, it think it makes sense to rule out the fuel system as the primary culprit. If there were any issues with the fuel supply or the carburetors, you would likely experience symptoms like sputtering or hesitation before the engine finally gave out. Right? The immediate shutdown without any preceding hiccups suggests that the problem might be related to something other than fuel delivery. BMW K75 dies out sometimes and wont start for a while 177381

    

15Back to top Go down   BMW K75 dies out sometimes and wont start for a while Empty Dies sometimes Fri Oct 13 2023, 07:01

daveyson

daveyson
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Spark plugs wet or dry?

You got sparks?


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Point-Seven-five

Point-Seven-five
Life time member
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The Hall Sensors are a fairly common source of trouble now that most of our bikes are getting over 30 years old. 

A good test would be to get a can of freeze spray and remove the plate that covers the sensors.  Go for a ride and when the engine quits try restarting.  If the engine won't start, then give the sensors a good shot of the freeze spray and try to start again.  If the engine starts after the spray, your sensors are bad and heat sensitive.   This heat sensitivity is a sign of failing sensors and they will need to be replaced.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
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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Point-Seven-five wrote:The Hall Sensors are a fairly common source of trouble now that most of our bikes are getting over 30 years old. 

A good test would be to get a can of freeze spray and remove the plate that covers the sensors.  Go for a ride and when the engine quits try restarting.  If the engine won't start, then give the sensors a good shot of the freeze spray and try to start again.  If the engine starts after the spray, your sensors are bad and heat sensitive.   This heat sensitivity is a sign of failing sensors and they will need to be replaced.

Added to this, do the reverse and when the bike is completely cold take a hair dryer [if you have one] to the T plate and make it hot hot. Then try start.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 49,200 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 63,390 miles

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

PhillipRambo

PhillipRambo
active member
active member
daveyson wrote:Spark plugs wet or dry?

You got sparks?
Havent checked my sparks conditions, but its a good idea! In the case of no spark what could be the issue then?

    

PhillipRambo

PhillipRambo
active member
active member
Point-Seven-five wrote:The Hall Sensors are a fairly common source of trouble now that most of our bikes are getting over 30 years old. 

A good test would be to get a can of freeze spray and remove the plate that covers the sensors.  Go for a ride and when the engine quits try restarting.  If the engine won't start, then give the sensors a good shot of the freeze spray and try to start again.  If the engine starts after the spray, your sensors are bad and heat sensitive.   This heat sensitivity is a sign of failing sensors and they will need to be replaced.
Thanks! I will try this next time i am in the workshop

    

daveyson

daveyson
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"In the case of no spark, what could be the issue then?"

Which plugs don't spark could help to point us in the right direction. 

The pattern seems to be related to heat, so as mentioned, the Hall sensors are a good fit with your symptoms. At start up (engine cold) everything is good. After seven minutes (engine hot) it stops. After a while (engine cooler) it starts again.

If the Hall sensors are good, a bad coil could be another possibility.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

j1s1

j1s1
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New member
Hej Phillip,
A short comment - when trying/getting new Hall Sensor - BUY THE ORIGINAL BOSCH. The cheap ebay/amazon/... once cost you a fraction of the original thing. And that will open up a can of worms like you would not believe.

If the one you have sitting in now is NOT an original Bosch. Start there. AND make sure you get the right one (there is more than one that fit into the machine - but only one version you should use - get the right one).

Drive. Be safe. Have fund (eller: "med hilsner fra djævle-øen")
Jensen

    

jkh

jkh
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Hej Philip.
My advice is also to use the hairdryer method to test on the Hall sensors. Your symptoms sound like it is intermittend failing Hall sensors. They fail when the engine gets hot. Gets back in working orden when the engine is cooled down.
Endnu en hilsen fra Djævleøen

Regards Jens


__________________________________________________
'93 K75RT - Previous bikes: '53 AJS Matchless, a lot of 70'ties Honda sohc/4's and some MZ's
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Personally, I prefer the freeze spray method because some heat guns can reach temperatures of well over 800F which is more than enough to destroy the Hall Sensors if one is not careful.  Even hair dryers are capable of damaging temperatures. 

There is no way the freeze spray can damage the sensors.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

24Back to top Go down   BMW K75 dies out sometimes and wont start for a while Empty UPDATE Fri Nov 03 2023, 08:16

PhillipRambo

PhillipRambo
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Hello guys, i have tested my hallsensor be heating it up and cooling it down. After i heated it up, it wouldnt start, and when i cooled it down it started again. I have replaced the hallsensor, witch i did by placing it exactly like the previous one was mounted. I was worried that i had to time my engine afterwards, but since i was very careful of how i placed the new one, it didnt have to. Now it starts and runs nice, also went it gets hot!, thanks for the help guys santa

    

Dai

Dai
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BMW K75 dies out sometimes and wont start for a while 212902


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

moriarti

moriarti
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HALLELUJH, Now buy 2 carry a spare, and ensure it never happens again  Very Happy Very Happy


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1984 k100 rs red/black VIN  0004449 Now sold to Olaf
    

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