BMW K bikes (Bricks)


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Quist

Quist
active member
active member
Hi guys

I am struggeling getting my K100 Rs from 1983/84 to start after a good old fashion shine up. 

The weird thing is that I drove the bike from the garage to my home (a 5 minute drive, nothing big) and it ran smooth as a baby butt. 
When I get home I changed the oil and oilfilter and try to start it again - and then it starts farting really weirdly. 

When I say farting, I mean that it may start and run for less than a second and then turns off, the starter motor and everything is trying to start it. 

My brother and I went through the SUPER helpful pdf and get to the point that there is nothing mechanically wrong, because as soon as we pull off the Water heat sensor OR the air flow meter it fires up right away and is able to idle (at a little higher rpm than usual - but stable) 

I changed the water heat sensor as it indicated in the pdf that the resistance was a little off (it was saying that it was colder than it was) and same result as before. 

(Side note. the oil pressure and heat indicator in the instrument cluster does not turn on before I start the bike, don't know if that is indicating anything)

I drove it home from the shop for crying out loud and then nope no more riding for you sir . . . . Help me please!

Best regards
David


__________________________________________________
Proud 1984 K100 RS diva rider
    

kennybob

kennybob
Silver member
Silver member
Welcome David

Did you all happen to clean the big bundle of grounds that attach to the frame under the fuel tank?  Sometimes corrosion builds up there and causes electrical malfunction such as yours.

    

duck

duck
Life time member
Life time member
Make sure the fuel tank connector is firmly plugged in.

They are known to get flaky so try wiggling it while you start the bike to see if that makes a difference. (Same thing with the ignition switch.)


__________________________________________________
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
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

Quist

Quist
active member
active member
I have changed the fuel pump thus making sure the cable there is firmly attached.
The grounds under the fuel tank are nicely bundled and clean as a mirror.

The funky thing is that it runs like a charm if you disconnect either of those two sensors. 

Thanks for the input guys!


__________________________________________________
Proud 1984 K100 RS diva rider
    

kennybob

kennybob
Silver member
Silver member
Maybe have to find a known-to-be-good jetronic unit and swap it out to test if the problem is inside.

Another approach is to open the cover and inspect for burnt components or cracked solder joints on the circuit traces for those sensors.

    

Quist

Quist
active member
active member
kennybob wrote:Maybe have to find a known-to-be-good jetronic unit and swap it out to test if the problem is inside.

The thing is that I have talked to a mechanic and he says that the odds of it being the jetronic that is gone bad i slim to non existing, but it is where I was getting at myself as well. :s


__________________________________________________
Proud 1984 K100 RS diva rider
    

kennybob

kennybob
Silver member
Silver member
Maybe slim odds, but it must be tested to verify it is good (or bad), otherwise how will you know what to rule out when troubleshooting?

i have repaired hundreds of failed Bosch motronic units--the biggest culprit is cracked solder joints due to vibration.  Motorsickles don't vibrate?

The other thing that comes to mind might be a bad temperature control unit in the electrical box under the tank--it seems to have common elements to the dash lights, the temp sensor, and possibly share a common ground with the AFM.

Do the headlights come on? horn and blinkers work?  Checked all the fuses?

    

92KK 84WW Olaf

avatar
Life time member
Life time member
Yours will have the bolted down fuel tank, with the single bolt at the rear.

The connector on the outside left front of the tank is a well known problem, it can be loose and you should tighten up the female connectors on the plug a little. I had exactly the same problem you have after a service and this solved it. The earth connectors under the tank are also an essential.

The Jetronic units can go wrong but if you do a search on eBay with the Bosch part no you will find brand new ones as the same unit for the 8 valve engines is also used in a Volvo 340!!


__________________________________________________
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 48,061 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 61,190 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
    

Quist

Quist
active member
active member
Kenny the lights do come on, horns and blinkers work as they should, but I am not questioning that the jetronic can be the culprit, I just want to rule as much out before getting one of those. I have found a source for it, but really nice to know that it is the same as the Volvo!! Thank you Olaf! Yeah the bolt is missing, and has always been missing since the previouse owner thought it wouldn't hurt it. 

I will check the fuel tank connector tomorrow in day light!

All fuses has been checked! 

I have ensured that it is grounded but I have heard that I may have to check the connectivity between the ground and the sensors, any thoughts and tricks on that?


__________________________________________________
Proud 1984 K100 RS diva rider
    

duck

duck
Life time member
Life time member
The temp sensor grounds when you screw it in. That's why it only has one wire.

The air sensor has a ground wire from the L-Jet.

Those should not be an issue.


__________________________________________________
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
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

92KK 84WW Olaf

avatar
Life time member
Life time member
If you are at the temperature sensor as far as I know that's on the left side of the radiator near the fuel pump wiring connector plug to the tank.....

If that bolt is missing the tank may bounce a bit and that may disturb the connections. The fuel tank connector may look a little brown, indicating heating/shorting issues.


__________________________________________________
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 48,061 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 61,190 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
    

Quist

Quist
active member
active member
Duck what you are saying is that i would either be the relay or the jetronic then?

The bolt is missing but the tank is being held in place by the rubber bushings in the front and the seat so not much moving around.
and if it is the connector to the fuel pump you are thinking about then it shouldn't work if I unplug the water sensor should it?

Guys I really appreciate your input! THANK YOU!! cheers Apparently unseen electrical malfunction 212902


__________________________________________________
Proud 1984 K100 RS diva rider
    

duck

duck
Life time member
Life time member
Whether the tank is bolted down or not has no impact on anything electrical and will not impact how the bike runs.


__________________________________________________
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
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

Quist

Quist
active member
active member
So duck you would suggest me to find and try another jetronic?


__________________________________________________
Proud 1984 K100 RS diva rider
    

kennybob

kennybob
Silver member
Silver member
i'm going to put my money on the L-Jetronic unit as the culprit because both the temperature sensor and the AFM are major input signals for the Ljet. 

It idles with either or both disconnected, but won't idle with both devices attached.

It was riding one day, then quit the next.

My guess is the signal conditioning circuitry (op amp) of the temperature signals for the water and the air.

    

duck

duck
Life time member
Life time member
Yes, swap in another known good L-Jet - but I wouldn't pay for one until you know that's it.

CPH is a pretty big town. Hook up with the local Beemer club or go to local online MC forums to see if you can find another K100 owner who is willing to let you try theirs.


__________________________________________________
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
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

Quist

Quist
active member
active member
Kenny and Duck you are awesome! I will let you guys know what happens when I find a unit to test it with!

Big thumb


__________________________________________________
Proud 1984 K100 RS diva rider
    

Holister

Holister
Life time member
Life time member
Quist wrote:Kenny the lights do come on, horns and blinkers work as they should, but I am not questioning that the jetronic can be the culprit, I just want to rule as much out before getting one of those. I have found a source for it, but really nice to know that it is the same as the Volvo!!
Be careful buying a Jetronic. Many vehicles of that era used the Jetronic but they are not all the same. They are mapped differently for each vehicle. You might be lucky to find a unit from another vehicle the same as we use in our K100s but I doubt it. I would exhaust easier to test and more likely possibilities first.

Post your VIN and we can find the correct Jetronic part number for your model.

I have ensured that it is grounded but I have heard that I may have to check the connectivity between the ground and the sensors, any thoughts and tricks on that?
You can test  earth connections by testing continuity on the FICU plug. Take a look at the Trouble Shooting link off the portal page. The test table is about 2/3 way down the page. For example between pin #13(earth) and pin #10(temp Sensor) if you read 'open circuit' (infinite resistance) then its likely the temp sensor is corroded and it's not earthing properly.


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
 Apparently unseen electrical malfunction Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

Quist

Quist
active member
active member
Hollister, I have found a jetronic from a vendor that says it's from a 1988 K100 so I think I should be good on that part, im not really interested in trying to navigating too vividly in intervehicle parts, specially not the electrical ones. 

I did the entire array of checks that is 2/3s down the pdf page, and there were no signs of any problems.


__________________________________________________
Proud 1984 K100 RS diva rider
    

kennybob

kennybob
Silver member
Silver member
So you went thru the flowchart on page 5 and worked your way down to page 20 of the 30-page troubleshooting guide (pdf file)?

And you tested the resistance of both the old and new water temperature sensors and compared with the temperature chart?  Were they okay or could both have been bad?

    

Quist

Quist
active member
active member
Kenny I went through the flow chart and came to meassuring the resistance on the water heat sensors. The old one was indicating that it was like 10 degrees Celcius colder, so I changed it, but didn't change on the original problem.


__________________________________________________
Proud 1984 K100 RS diva rider
    

Laitch

Laitch
Life time member
Life time member
Quist wrote:My brother and I went through the SUPER helpful pdf and get to the point that there is nothing mechanically wrong, because as soon as we pull off the Water heat sensor OR the air flow meter it fires up right away and is able to idle (at a little higher rpm than usual - but stable)
When you do that disconnection, David, can you rev the engine?

Both Kennybob and Duck have alluded to a faulty Jetronic, and the more diagnostic steps you take the more it seems to indicate that area.

I'd be tempted to pull the Jetronic plug and thoroughly clean the plug and the pins with Deoxit or another electronic cleaner to be sure there isn't some fine material that inadvertently started bridging the pins—unlikely as that would seem—then reattach it firmly

That's my magical-thinking approach toward a less-costly outcome.

    

Holister

Holister
Life time member
Life time member
Quist wrote:My brother and I went through the SUPER helpful pdf and get to the point that there is nothing mechanically wrong, because as soon as we pull off the Water heat sensor OR the air flow meter it fires up right away and is able to idle (at a little higher rpm than usual - but stable)
When you "pull off the water heat sensor" what are you actually pulling off?


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
 Apparently unseen electrical malfunction Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
I may be very wrong, but I seem to recall that at some temperature the engine control unit shuts down the engine.  It could be that a problem in the sensor is making the engine control think that the engine is overheating.  Or possibly, the temperature control relay is malfunctioning. 

Maybe someone more knowledgeable than myself can take this further.


__________________________________________________
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
    

duck

duck
Life time member
Life time member
Point-Seven-five wrote:I may be very wrong, but I seem to recall that at some temperature the engine control unit shuts down the engine.  It could be that a problem in the sensor is making the engine control think that the engine is overheating.  Or possibly, the temperature control relay is malfunctioning. 

Maybe someone more knowledgeable than myself can take this further.

If the temp sensor wire is chafed along the way somewhere and shorting to ground then the L-Jet will think that the water temp is a Brazilian degrees.

The temp sensor resistance to the L-Jet can be measured between Pin 10 on the L-Jet connector and ground. At room temperature (68F or 20C) it should read about 2.5ish Kohms.


__________________________________________________
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
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

Holister

Holister
Life time member
Life time member
Quist has said that he's done those tests on the FICU plug from the Troubleshooting page, but without any values posted it's hard to make a qualitative assessment.


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
 Apparently unseen electrical malfunction Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

Rick G

Rick G
admin
admin
The ECU wont shut the engine down if the temperature gets too high but if over 113°C it will prevent the engine starting by preventing the injectors from firing.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

28Back to top Go down   Apparently unseen electrical malfunction Empty Eureka! Sun Apr 23, 2017 12:38 pm

Quist

Quist
active member
active member
Long due conclusion on this matter, after the first succesful ride where it actually works!

It seems that even new stuff can break. 

I changed fuel pump and filter before my last ride, and as it turns out, the ride home from the garage was enough to break the fuel filter, causing my headache...

Thank you for all your replies, and now I have a fully functional bike again!


__________________________________________________
Proud 1984 K100 RS diva rider
    

blaKey

avatar
Life time member
Life time member
Thanks for letting us know of the successful outcome.

We you say the filter broke, can you tell us exactly what "broke"?


__________________________________________________
Neil
K100RS 1986 RED!

Dress for the ride and the potential slide.
    

Inge K.

Inge K.
VIP
VIP
blaKey wrote:We you say the filter broke, can you tell us exactly what "broke"?

I would guess it did split in the seam, it was a big batch of OEM filters with
a weak seam which entered the market around 2000.


__________________________________________________
Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

blaKey

avatar
Life time member
Life time member
I knew about the bad batch of filters...but that was years ago! I would have thought they weren't around anymore. Shocked


__________________________________________________
Neil
K100RS 1986 RED!

Dress for the ride and the potential slide.
    

92KK 84WW Olaf

avatar
Life time member
Life time member
Its a good ending but......

Never assume that the dodgy parts in the system have all been used out. We had a similar thing with motorised valves in central heating systems and having to go into whole developments and pull them all. A bad batch coming in. But the annoying thing was the darn suppliers kept selling off the old stock even after they knew they were going faulty.

IngeK as always a fountain of knowledge!


__________________________________________________
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 48,061 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 61,190 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
    

Quist

Quist
active member
active member
blaKey wrote:We you say the filter broke, can you tell us exactly what "broke"?

I decided to cheap out on the filter, as I bought my fuel pump from them as well - Shouldn't have done that!

Lesson learned. Smile


__________________________________________________
Proud 1984 K100 RS diva rider
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
So, how did the filter break?  Was it at the seam?  Was there a manufacture date on it?


__________________________________________________
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
    

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