Need a bit of advice

I’ve purchased a 1985 K100RS for a charity bike ride from London to the South of France (and hopefully back). You know the type of thing, max budget £500, challenges along way etc.

Bike had been standing unloved outside under a sheet for a couple of years, a lot of TLC it now runs.

I’ve found the info on this site excellent and could not have got the old girl running again without it, so thanks to all who contribute.

Problem is when testing at idle I noticed that I had never seen the cooling fan running although never ran her for very long. Not wanting to cook her I followed the test procedures that Jeff posted but have come to a dead end.


Ran the bike at idle for 20min fan didn’t come on.
It was about 5 degC in the garage but radiator and hoses to hot to touch.
Left her overnight to cool down. It’s just above freezing today,


Tested the fan by jumping relay connections 15 and A2, fan ran ok.
Checked resistance between E and 9 but appeared to get an open circuit
Disconnected temperature sensor checked resistance across terminals, got (9.7K),
Jumped sensor connector - fan didn’t run
Cleaned all connections, no joy
Checked continuity between 9 and sensor OK
Checked continuity between sensor and connection 10 on the EFI female connector - OK
Checked resistance EFI connector 10 to ground (4.8K)
Checked overheat light - OK

Resistances seem high but it was cold overnight, but can’t explain why no resistance between E & 9 and why jumping sensor connector didn’t work


Any suggestions?

I think that I can point out one mistake:
You jumped the sensor connector expecting to have the fan starting.
The two wires going to the water temperature sensor are one for each sensor. (the water temp sensor is a double sensor).
Unplug the sensor again.
With the ignition ON,
Ground pin E of the temperature unit. The fan should start.

The connection of the sensor has 2 violet/green wires.
At this connector, locate the one going to the temperature unit. (The other one goes to pin 10 of the EFI unit).
Ground it, and the fan should start.
If it does start, it points to a bad water temperature sensor.

Hi sorry i cant offer any help regarding your problem , i have too many
of my own ! , Ive just purchased a 1988 LT which has seen better
days ,, which im trying to prepare for a charity ride , also from London to
the south of France , Melee to the Med , Help for Heroes . ???? regards Archie

Hi Archie
Same charity ride mate. Got mine end of November, everything rusted up and some wiring problems. Spent a few weekends covered in oil and petrol and got her running, before the weather put a stop to the work.
She should be reliable by April (I hope) but haven't tinkered with a bike for many years so steep learning curve - I'm loving it.
Good luck with the LT
See you at Dover. Martin

If there is one thing I have found to be of the utmost importance with an old K model,[mine is an 89 LT] it is the importance to clean ALL the electrical connections on the bike from top to bottom.
First I used a Electrical cleaner to remove all corrosion and then an Electrical sealer to keep things clean for a long time [untill next inspection]. This advice was given on this forum and saved me a small fortune as all my Electrical problems were resolved.


BIG D

For those of you going to do the charity ride, I would like to get more information and I will try to promote it on the biggest BMW forum in France.
I will certainly be able to give you some contacts if you are in need of assistance or simply want to meet some French BMW riders.
Please send me some details by private mail.

Bert

Good on you you are on the right track and as noted by Big D the electrical connections need to be 100% since they are in the case of sensors like air flow and temperature are only passing small signals and it does not take much of a bad connection to totally mess things up.
Regards,
K-BIKE

Can you give a link to this event? sounds interesting, might be up for it too.

Thanks to all for the advice.
Sorted problem with the fan. Dodgy sensor was the culprit in the end. 1 fault down, about 50 to go.

Badgerdid - The charity event can be found on www.britishbiketours.co.uk web site - melee to the med.

Main event is raising money for Help for Hero's. I will be riding on behalf of a cancer charity for a close mate. He and I spoke many times of riding to the south of france together near the end so this event felt right.

CF - thanks for your kind offer to promote the event, details can be found on the above web site, or alternatively visit www.justgiving.com and search for martin merritt.

Archie and MGM; I think you are both doing something really commendable and am willing to support you. Not financially, but with time, knowledge and support getting these bikes ready. If you PM me I'll give you my telephone number and would be quite happy to talk you through the K-bike technique and share experience. Cheers, Rene

Well boys and girls, I tried my best to make a set of bushes (from and old set of starter motor bushes - with a Dremel)

I used a 2 part epoxy to remark the housings for the bushes.........

It all went back together well - but, I could not get continuity between the two terminals, I suspect I did not make a sure enough connection between the brushs and the terminals .  . . . 

K Bike cooling system brushes





Oh well - I tried,,,,,,

I got a 12V 3100RPM electric motor with very similar dimensions off the net today for $31 AU delivered from Hong Kong.

I will post the results.....

good luck marky

there are alternative fan assemblies available also ...might have to make a bracket to fit up to the radiator though

and some of them have a better throughput of air flow as well lower profile for the motor assembly ...amazing what 20 something years of development produces to everyday things we see now .


cheers

charlie99 wrote:good luck marky

there are alternative fan assemblies available also ...might have to make a bracket to fit up to the radiator though

and some of them have a better throughput of air flow as well lower profile for the motor assembly ...amazing what 20 something years of development produces to everyday things we see now .


cheers

Thanks Mate....

the fan I have coming appears to be almost the exact same size as the original one - I shall just have to cut off about 2.5cm (1 inch) from the spigot.

I am a little concerned that it only spins at 3100RPM and not 4500RPM - (It gets hot in Brisbane) well shall see.

For those that have the same problem, if this works out I will post link to motor purchase and photographs of the replacement process.......

Don't worry too much about the RPM difference, as fan blade design will have a huge effect on how much air the thing shifts.  Fit it and see whether it works - you might be lucky.

Hi,

Firstly I will confess my failure incase you are thinking the same thing....



Next !!!!!

1.        Buy one of these:-
http://www.ebay.com.au/itm/DC-12V-0-9A-3100RPM-MIN-Rotary-Speed-2-Wire-Cable-Gear-Motor-/301193482990?ssPageName=ADME:L:OU:AU:3160
$AU32 in hand (Brisbane - Australia)
       Remove fan from spigot on original motor. It just pulls off….
2.       Take note of the clearance from the end of the spigot to the flat plain of the housing outer face – see photo.
   



 
3.       Remove original motor from plastic housing and get rid of the ridges inside the housing so that the new motor fits all the way home. See Photo.  You will have to make a hole at the end of the original housing so that the new wires can come out. (I used a Dermal)



4.       Once new motor is seated all the way home, and it will fit well. Use a straight edge to work out how much you need to cut off the end of the new motors spigot. See Photo.  Once again I used a Dermal.

5.       Drill out the hole in the middle of the fan to allow the new spigot to fit – don’t go to big – it needs to be a tight fit.

6.       I used silicon to mount new motor back into original plastic housing, it fits very well – See photo. 



7.       Push fan onto new spigot – make sure that it can spin freely when fan is placed face down on a flat surface or it may munch into your radiator (not good).
 
8.       Be aware of the polarity when reconnecting the wiring – remember you want the fan to SUCK not BLOW, this means you may need to swap the red and the black wires over to get the right air flow direction out of the DC motor.
For those of you that are more Technical than I – note – the new motor is specked at 3100RPM, the original is specked at 4500RPM. If someone sees a big problem with this please let me know, I life in very sunny very hot Brisbane Australia – if anybody is going to have a problem with the slower fan speed then I guess it will be me – I must say though – she really sucks! I do not see a problem.
I hope this helps – I know I had a big problem buying an original motor knowing full well the design is floored to say the least (and no replacement brushes!) Not to mention the cost…….

Keep the shiny side up boys and girls…….

The above Mod works beautifully.

I can do traffic now......