Been searching forum for similar problems and can come up with sort of but not exactlly my issue . Bike has been running beautifully for several months now . Have been going into forum and followed the deoxit advise and other suggestions that I see as helpful . Will list what I have done up until issue has started very recently . New battery and cables , (good grounds) , fresh correct plugs , new fuel filter , replaced the radiator temp sensor , this reactivated the fan . Fresh tires , deoxit on any electrical lead that I can pull . Fresh oil and filter . Bought the bike from a seller on Ebay and have been slowly going through this to correct defects . Bike starts and ran great , excellant fuel economy . Have been on several long distance rides with no issue .

Hopefully this will paint a picture . Went out on a short run with daughter recently and bike just died while moving like we lost spark . All electrics still working fine . Starter would turn ,lights all function , switches in correct positions . Dead as a fieldmouse in the cats jaws . Drag bike home and curse alot . Next day try it and she starts right up ! Bike will run about 5 minutes and then just cuts out . Let it sit with a cooling fan on shroud and it will start and run normally until reaching a tempeture that it does not like then will cut out and die . This process can be repeated . Have good spark even after cutoff and seems like I have fuel pressure because while cranking over to check good spark I caught a dragons fireball from cylinder onto my hand . Noted a bit of blue white smoke from tailpipe when it does run but figure this is some flooding . Will check fuel flap tank vent idea next . How about a couple of ideas to follow up on please ? Think I have a heat issue that is shutting down a relay Looking for some ideas here in Norman , Oklahoma US of A

Hi Norman. That seems like an overheated hall sensor to me. Search the forum for testing of the hall sensor, there's quite a bit on it. If it is failing, the sensor can operate fine a low temps, but as it heats up, it fails until it cools down again. Something to look at anyhow. Good luck.

Thanx for the tip , have seen some suggestions with the hall sensor in forum . Guess that I need to take a heat gun to this . Will read up on procedure . This sounds expensive but if it breaths life back in to machine so be it .

beemerboneyard.com for used parts...

http://www.kbikeparts.com/
Here's another place for used parts. Hope your troubleshooting goes well.

Was able to replicate problem by applying some heat with my Harbour Freight 8 dolla heat gun . Put the heat to machine and she started running crappy and then shuttoff sooner than previously . Looks as though the Hall sensor is pretty suspicious to me .Will goto radio shack tomorrow and do the LED test as suggested in the forum lectric problem shoot area to confirm . Muchos gracios to whoever you be for the suggestions . Hope to be up and running again in the heat here in the Heartland .Nothing like a 104 degree ride yeehaw !

As you say you got a good spark even after cutout, it seems like it`s not the hall sensors that is the problem.
But I do agree that it is a typical hall sensor problem symptom.
When you tested for spark did you test both 1,4 and 2,3?
(different hall sensor signal each coil).

If it afterall should be a bad hall sensor, you can change out the hall sensor as a single part (Honeywell 2AV54), if you`re a bit handy.
Far cheaper than changing the whole unit.

Another thing check that you receives the correct signal from your new coolant temp. sensor at the FI ECU connector (pin 10) when the engine is hot.
A graph which shows what you should expect at different temp you find at CF`s troubleshooting guide at the portal.

Should have adjusted my post..........after your new find..........but some could become useful..........

To my knowledge overheated water sensor or a controller that thinks it is overheated will not kill a running engine, it lights the light and runs the fan but only stops you starting if you turn the engine off. That was an intentional safety feature so an overheat will not cut your engine out on the road.
Regards,
K-BIKE

I never got any problem with this sensor or overheating, so I ain`t got any real life experience with this overheat protection feature.

So my knowledge to this is only what I`ve read in different forums, and the posts from those who got experience with this feature.

And I understand that it is a two step function, and if the temp continues to rise passed the set limits where you can`t start, it would cut the fuel on a allready running engine.

i have a bypass switch on mine inge ....takes the temp sensor direct to ground (input from sensor )

it doesnt take any action other than turn the fan on ...and a failed start after ignition switch off and restart

As said it`s only what I`ve read...........and my grandmother told me that I shouldn`t believe all shit I did read everywhere.........the only true story was in a book that she got.

But since both the fan starts, and it won`t start...
Have you grounded both elements in the sensor?

To start the fan it should be enough to ground the element which is connected to the heat management relay.

yep your right the fan wont start after turn on ...have to have the motor running ..i must have still had my tempsensor issue when i did the mod or something , but the engine does start up ok with that mod ....

That you need to have the engine running is quite normal, as power to the heat managent relay switch contacts (to the fan) pcb is feed from the FI/fuel pump relay.

The fan is not on the same sensor as the overheating sensor and a friend of mine his K100 stopped dead when it overheated and left him in the middle of Parramatta road (Sydney and 6 lanes each way). That is the only one I have heard of and as k Bike said it only won't start but it shouldn't stop it so I can't say for sure.
Just because the fan sensor is short to eth doesn't mean the ECU is getting an overheat signal.

I am finally able to get back after bike problems . I have a K100 that just flat shuts down after about 5 minutes of run time . Let it cool and she fires right back up . Have tested the hall sensors they showed bad so I wired in a new set . That was a mind bender ! Made some index points as reference for timing and intend to use this to do a by the ear timing . I had also replaced temp sensor and have been running with it up to the shutdown point where bike just quits . OK bike fires right up with new hall sensors and shuts right down like before . I am trying to now figure what you guys are going on about to test next in the troubleshoot tree . I go out and hit this thing when parts and time are available so its hit and miss with my correspondence . Any suggestions next and I will be digging into your troubleshoot pages also thanks Dale Goodman

the best place to test the temp sensor is at pin 10 in the under seat (injection computer )

do you have a temperature guage fittted ? it might be that the thermostat isnt opening up propperly ....the fluid bypasses the radiator till it comes up to temperature ....the thermostat is suposed to then block the bypass and direct flow through the main core of the radiator ....given that the impeller is all working correcctly ...etc

have you actually observed flow through the cooling system ?

just some thoughts that might help before you go digging around in the ecu area under tank

you mentioned blue white smoke as well .

after my weekend visitors experience ,,,have a look at the fuel, filters etc in the tank , could you have picked up a bad load of fuel as well ...im thinking water in the tank ...that picks up and fills the filter after a while ...cant hurt to look .

Hi Dale, The place I would be looking next is the plug point on the Ignition Control Unit which is under the tank up front and under the top frame tube. Check for corrosion at the plug and make sure it has earth on pin #1. Also check the earth connection on the frame left side just back from the ICU, make sure it is clean and tight.

If that's all OK you might want to open the ICU (the one under the frame tube). The first K's had at times issues with humidity/water in those units. Far fetched last resort kind of check, but if you haven't found it meantime.......

I seemed to have similar problems except that after the cut out starter was not functioning at all, though once or twice it did turn over.

The problem disappeared after I replaced the ICU under the headstock. Motorworks £50 plus VAT. When I got the unit I cleaned off all of the contacts with 1200 wet and dry used dry, they looked really good and reassembled the electrics. The problem has not reoccurred.

I still have the old ICU which I intend to check out. I opened it up and there was no evidence of any damp or water penetration anywhere despite its age and location.

Inge is an encyclopaedia of k nowledge on these.

92KK K100LT 193214 wrote:I seemed to have similar problems except that after the cut out starter was not functioning at all, though once or twice it did turn over.

The problem disappeared after I replaced the ICU under the headstock. Motorworks £50 plus VAT. When I got the unit I clenaed off all of the contacts with 1200 wet and dry used dry, they looked really good and reassembled the electrics. The problem has not reoccurred.

I still have the old ICU which I intend to check out. I opened it up and there was no evidence of any damp or water penetration anywhere despite its age and location.

Inge is an encyclopaedia of k nowledge on these.

There is a guy here in Oz who fixes the ICUs and removes the rev limiter so don't throw it out.

Rick G wrote:.

There is a guy here in Oz who fixes the ICUs and removes the rev limiter so don't throw it out.

Any idea what he charges Rick?
88

88KE wrote:

Rick G wrote:.

There is a guy here in Oz who fixes the ICUs and removes the rev limiter so don't throw it out.

Any idea what he charges Rick?
88

No idea but here is the address http://www.cdirepair.com.au/

Well , I finally got to garage and with ohm meter and troubleshooting guide in hand . Went after the EFI module connection first (cause I didnt wanna pull tank again ,due to the fact I have numerous not meaning to rape my fuel tank paint job last time I pulled it evil teenagers ). . Wanted to thenpull tank and ohm /test ignition control . Couldnt reproduce too many of the values specified on the graphs given in the troubleshoot guide for EFI . Had bike start and run very nicely for some time after terminal reconnect. Note that I replaced both Hall Sensors previously and wired them in . Bike now has lost all spark , before I just could not start until cool down after a 5 minute run time . Now I have really killed the cat . Also of note thought that the fan was operational . It is not receiving a run message . Put 12v across it and she spins . Question can we test the relays under the seat individually ? Am suspect of the tempeture sensor relay talking to the fan with power . Will now have to figure where spark decided to hide . Also note that I wrote the company that does the ignition control unit repairs and my unit would be about 325.00 USof A dollars . Will check to see posts later going on a camping trip with evil teenagers to see a million bats . Selmon Batwatch in a place called Freedom , Oklahoma . Thanks for the help so far Dale Goodman

Hi Dale,
Let's get back to basics and start with the troubleshooting ladder diagram that is in the download forum. Note to all we don't post links to the download pages in the open forum to prevent others who do not have access trolling through especially the bots who collect links.
Work down through the troubleshooting list and tell us what you find the chart is good because it takes you through a series of go no go tests.
Regards,
K-BIKE

Will try and follow in a more orderly fashion . I was trying to go for target areas and pursue the troublespots . Am a flight controls specialist and have to do a significant amount of whats causing this to happen on a daily basis . Will post as we find things . Waiting for a bit of cooling and we are going on a trip out to western Oklahoma today . Current temp is 108 F and we are headed to hotter ! Thanks for the attention Dale Goodman

Good Luck Dale
keep away from those bats mate (and evil teenagers for that matter) our Queensland friends here have a specific deadly virus that comes from the little buggers.
Try and keep cool
RT

If you ever get a chance to go see bats and have access to an ultrasonic sniffer which changes ultrasound to audible take it with you the sound of the bats echo locating insects in dusk is amazing. I used to take mine to a camping ground in Devon where there were a lot of bats and the sound was fascinating.
Regards,
K-BIKE

Back from my bat visit and now going to a rodeo in Pawnee , Ok . Been really busy and then lets talk about the 113degree ambient tempeture outside melting my thermometer ! Was able to go out and start some toubleshooting going down the list provided on the site . Followed tree down to Electronic module bad ? The unit which I have not tested thorough yet is pn 0227401001 I have aquirred for a whole$ 10.00 a 0227401003 unit which I had been told would work . Figured for the price that I got it for Could just resell for a profit if she wont work . While testing the EFI LE- Jetronic test was not getting many of the values that are listed . Looked upstream on the schematic and the tie in is the Ignition computer . What say ye of the troubleshooting advisers of the board . Do you think the 1 digit difference in the computers will matter as far as swapping them out ? Anybody object or what else can I look at ? Still have not found my spark yet either ! So hot that I can only hang out in early morns to try and troubleshoot .

Don`t know which kind of Zündapp model you own, but.....
Your first part # (001) is for a K100 (4 cyl.).
And the second (003) is for a K75 (3 cyl.).

I have the 4 banger . Looks like we have a cylinder shy model 3 cyl computer . Was told by the seller that it would fit and the price was good . Ebay will have it soon . Thanks

Hello everyone,
I had a similar issue with my 85 K100RS that I had purchased from a Rolls-Royce jet engine mechanic. The bike was in great shape and this guy had taken great care in maintaining it. I was hopeful the bike would not have any major issues. Low and behold, the day after I bought it, the engine cut out while cruising down the highway. I called the seller and he was shocked! He came to pick me and the bike up (this guy was super) he troubleshooted a few things, got it to start again, took it for a ride, no problems. Thinking all was good, I left for home, and wouldn't you know it, the same thing happened. Anyways, to make a long story short, I found that the problem was simply that the cable leading to the ECU was not fully engaged. The mechanic had changed the battery just before he sold it to me and didn't quite get the pin clipped in all the way. I've had about 3000km trouble free riding since this happened last summer.
I hope this helps.
Cory

Will try and get caught up here . Had family issues , kid stuck in China , daughter running off with boyfriend a fatherinlaw heartattck and then record heat . Finally got back after bike . I aquirred a box of old relays from Ebay , the on line troubleshooting guide and my Haynes manual . After swapping the tempeture relay my spark returned but the bike would still only run until reaching a whatever warm tempeture then it dies again . Let it cool and she runs . I swapped out the FI relay and the fan worked and bike does not die . After a day or so I returned to garage and wanted to zero in more on throttle and timing . I do not have depth gauges so was using the earball method to tune the timing . I had previously replaced the Hall sensors and wired them back in . Plate has been indexed so this was used as reference . Was able to get throttles closer , 1000 rpm idle and timing response was better . The fan stopped working again and the bike warms and then dies has returned . I believe the problem is in the cooling fan , FI relay , tempeture control area . I am leaning towards a FI relay problem being that when I replaced it before I had a good extended run time with cooling fan . I will try and run the logic tests again on this replacement relay . Any ideas on further testing to zero in on this issue Dale Goodman

That your fan don`t function could also be caused by a malfunctioning load shedding relay.
Then you also would loose the head/tail light and horn and got weird flasher behaviour.

In my box "o" relays should be another load shed relay . Will drop that in today . Bike still has good lights and no other problems that are described in a load shed relay issue . What is frustrating is the fact that one day we have a good consistant run and then the next day its semidead again . I definatly have a problem in the heat sensing circut which cuts out the ignition .When the fan was working had good start and run conditions . Have not physically pulled out thermostat and tried it yet by heating in water . Can an alternate thermostat be used such as an automotive part number ? If one is available and not a gazillion dollars its just as easy to drop in a new one . I am probably introducing some of my own issues by digging into the machine so much but I am also learning it more thorough also and correcting what is out of whack . Thanx for the advise and will keep looking for some more suggestions in forum areas . Got a brother in from another state visiting so we are entrtaing this family . To top that my boomerang runaway daughter has shown up at house again ! :suspect: Time to meet the love of her life boyfriend that she has now known for 4 weeks .....................................Dale Goodman Oklahoma , USA( its still hot here)

Your problems are probably more related to the temperature sensor, the temperature switch and the wire connections thereof. That arranges the working of the fan and warning light as well as giving input to the ECU re the fueling.

Bueno Hombre wrote:In my box "o" relays should be another load shed relay . Will drop that in today . Bike still has good lights and no other problems that are described in a load shed relay issue

Then the LSR is confirmed OK, no need to change. ....just did mention the LSR, if..........

Does the high temp warning light show before the engine cuts?
If, check the fan related circuits.
If not, check the sensor related circuit.

Anyhow, the problem could be the relay itself.
To test the relay, remove it from the socket.
Add 12V + to terminal 9.
Add 12V - to terminal 31.
Then when adding 12V - to terminal E, you should hear the relay click.

[quote="Inge K
Anyhow, the problem could be the relay itself.
To test the relay, remove it from the socket.
Add 12V + to terminal 9.
Add 12V - to terminal 31.
Then when adding 12V - to terminal E, you should hear the relay click.[/quote]

do you mean earth to terminal E inge ?

charlie99 wrote:do you mean earth to terminal E inge ?

-, earth, ground, negative, minus...........choose the one that suits best.

Swapped out the load shed relay . This has no effect motor still goes to cutout . Let it cool and we have a run condition . I had tested the first FI relay already and had a good click , actually took the cover off and watched the points close . Put in the second FI relay from my box "o" parts and thats when the fan worked and we had a good run condition for a day . Next day brought back the sadness no fan and a short warmup and then engine cutoff as before .I had changed nothing nor even raised the seat . Will go out and check the new FI relay for the click next stop in the garage . Beginning to wonder if I have a stretched or broken wire in this circut . Problem must be within the area of tempeture sensor relays to the computer . About the only thing not replaced from Ebay online parts shopping is the fuel managment computer . I can find an inexpensive thermostat locally or get the correct BMW one for about 50 bucs . Apparently the character that I bought the bike from just slings them together and puts them on Ebay , Along comes a big dummy like me and its saletime ! Have bought several bikes off Ebay and had better luck before . Gonna go out and sacrifice a bucket of chicken and burn some incense maybe a norse god of blunder will feel mercy and the bike will live longer than a 5 minute run . Gonna go do some drinking now with family and get back to bike in morning . Thankz mate for the advise will keep hunting till we find this problem . Dale Goodman yes its still hot in Oklahoma :cherry:

Since it make a difference in the fan function to swap FI and HM relays with dittos,
I`ll guess it could be a bad connection between these two.

The FI relay feeds the HM relay pcb, check the circuit between FI/87 and HM/9..... especially after fuse # 6, since it seems like your fuel pump runs w/o problems.

Also check the connectors in the relay sockets.
I guess you allready have noticed that the FI relay have a double output.

deoxit ...deoxit ...deoxit ...do all those plugs and sockets around the relays ...

Morning clean after some brewskies .You oughta see the mess a pack of kids and relatives can make ! Yuk , get the hose out . Gotta do more relative entertaining today and then will hit bike again when its good and miserably hot . I like the idea of checking between relays will do that after the FI relay "click" check . Have already DEoxit through this whole area , that stuffs expensive at Radio Shack ! Guess that I will get some more , Bike came out of South Florida sea spray area . Have not really noted any significant corrosion as I dissasemble though . Buff connections with a brass brush as I go . Want to get the gremlins out of this thing before the fall rides start . Have some interesting places planned . Not that hot yet in Oklahoma (cause its still morning ) Dale Goodman

Bueno Hombre wrote:I like the idea of checking between relays will do that after the FI relay "click" check

About the earlier mentioned relay check, I did have the HM relay in mind.

Been a week since I was able to post but have been busy with the Ohm meter this morning . I have checked the suggestions given earlier for the circut between FI/87 and HM /9 relay after fuse #6 this is good . I have put a brand new temp sensor in bike several weeks ago and this has had no effect so I am discounting this unit as a problem child . I can put power across A2 terminal at temp sensing unit and fan spins real nica like . Put power across terminal 9 and ground terminal E @ temp sensor again and with switcth in on position , fan spins like a top . I have tested and swapped out from my box "o" parts everything but the fuel injection control computer. Have not found an affordable one on Ebay yet . The best that I can surmise is the computer provides a ground when the tempeture rises to a predetermined level probably through the NEW temp sensor . When ground happens the temp sensing switch completes a circut that fires the fan COOLING then happens . My fan does not run because it gets no signal from computer .Bad computer ! The protection from overheat circut now comes into play and the machine shuts down until it cools off . Also found lots of really screwy wiring done by the guy that Had supposedly restored this bike . Have been correcting these problems . Yes I have DEoxit ..deoxit ..deoxit atized this thing brushed and cleaned etc . Will locate computer on Ebay or wherever .. Noticed the bloke that sold me bike is on Ebay selling parts might just tell him of my troubles . Any other tests that I can do to the computer or more suggestions ? Dale Goodman

In this issue changing the FI ECU would be to throw away money, since the the ECU doesn`t supply any signals to start the fan.

Hav you checked that you got a good connection between your new sensor and the E terminal at the relay?
It is also a 4 pole connector between the engine harness and the chassis harness.

The fan should start when the resistance at the sensor comes down to ~175 ohms.

nods head with inge ....first place to look ....

you should be able to measure from "e" terminal to earth for a change as heat increases , the resistance should decrease

Will go out and put tank on again and do some resistance measure at pin E . Going to leave relay plugged in and measure resistance to ground @ this point . Gotta put tank back in AGAIN ........ Must be a yo yo as much as this is going off and on ? Got lots of Emails going now fixing this and finding parts for my box "o" parts . At 175 ohms fan should work . I have tried unplugging this connection before and had a no run / start with this before . Dale Goodman Hey You guys wanna beer if we solve this ?

Bueno Hombre wrote:Will go out and put tank on again and do some resistance measure at pin E . Going to leave relay plugged in and measure resistance to ground @ this point .

I`m not quite shure if you get the correct values with the relay connected, as you then also would read the resistance to ground via the various components at the relay pcb. The 175 ohm value is based on the resistance on the sensor itself.

Bueno Hombre wrote:At 175 ohms fan should work . I have tried unplugging this connection before and had a no run / start with this before .

??

Bueno Hombre wrote:Hey You guys wanna beer if we solve this ?

Yes, please.

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I would suggest that you have most related stuff temporary fitted, run the bike on idle untill it stops...remove the relay, and measure at terminal E in the socket.

just extend your fuel lines a little , you should be able to run the bike with the tank suported a bit above the frame to gain access with the pump connector outside the frame .

with out all this on off stuff.....till you get it solved at least ....you can buy cheep fuel line for this purpose as we're not going to use it forever ,,just make sure the high presure line seals up well , actually i have a butterfly type hose clamp thumb twist on my high presure side ..for easy removal ..just havent installed one on the return line yet ...(put it on the list i guess )

there may be some interaction between the relay load and the resistance measurement ...so may be an idea to check the terminal on the connector side to earth after a run up to temp