Hi, I have a problem. How to set the potentiometer. K 100 RT 1984th thank you

Hi bohumil,
Are you referring to the mixture potentiometer? Why do you think it is wrongly set?
Regards,
K-BIKE

rt friend's not cold now, I tried the. water temperature sensor o.k injections o.k. new spark plugs, fuel pressure o.k. Hall o.k. new air filter, cleaned air weight, power-ok, fuel ok.

Hi there.
Youll find in tne web articles regarding the matter, from wat I´ve read the potentiometer is related to the air/fuel mixture. Due to aging the spring relaxes and the vane opens more with less air flow, this causes the mix to be more rich. You can correct this by trial and error stiffening the spring.
Hope this help.
Best regards
JAP

Sorry Mate, you'll need to tell us a bit more.

Hi bohumil,
What is the problem, is it no start, poor running, sooting up the plugs? Once we know what the issue is we should be able to help. If it is the mixture control you have a problem with unless there was a bad connection I doubt it would shift enough to be a real problem without someone having been twiddling it. More information please
Regards,
K-BIKE

Guys trouble is to start the cold bike. I have to try it many times (sometimes till battery is almost dead) to start it. Once the bike is not cold (after couple of miles) trouble is gonne and it starts perfectly. But the next day it is again hell to start it cold.

Was this a sudden change which happened one day overnight or has it got progressively worse?

From memory the starting mixture is set by the air temperature. First thing I would do (and you have probably already done this) is check the resistance values at the last point on the system so check the Hall Sensors at the ignition unit, the temperature at the the control unit, that way you check the cables all the way back to the controllers as well as the sensors.

Worth checking the ground connections throughout and also clean all the relevant plugs and sockets on the route from the sensor right back to the controller and clean the controller plug and socket especially well using DeoxIT and the little applicator sponges.

I have been amazed at how much dirt and contamination that has come off what I considered as clean contacts which had been well sprayed with contact cleaner when I gave them a thorough clean with DeoxIT on the applicator sponge.
Last thought is your compression OK on all cylinders when cold?

Regards,
K-BIKE.

Hi Bob,
With your knowledge of bikes and that workshop of yours (not to leave out a beautiful wife) You must have a real problem.
Have you tried a bump start? If it starts OK then, we would have a better idea of where to go.
Don't let your battery get too low or you will have relay problems.
Ajays

Pull the starter motor and check the brushes...if in a bad state it will cause a lot of unrelated problems.

a recent post by oldgoat mentions the fact that his connections to the afm (airflow meter ) were particuarly corroded ....in as much as he couldnt measure the values properly untill he did a clean up of the connectors ....this sounds like a good idea and worthy of doing to eliminate this as part of the issue.

K-Bike,
Just excellent advice on checking the sensors AND the connections going back to the controllers! I will be applying this new found knowledge this weekend.
Thanks!
OG

Hi OG,
I was as I say above, amazed at the dirt that came off the pins in the main module, I had previously given them a good clean with Electrolube contact cleaner and was well satisfied that they were clean.

Having finally found the one true path of using DeoxIT I cleaned them again using their little applicator sponges on a stick which can get in and clean the contact without the abrasion & scratching that one would get if using abrasive paper like fine emery.

I was absolutely amazed to find the black muck on the sponge which came off after I had treated them with DeoxIT and let them sit a few minutes. I was using a DeoxIT soaked sponge and gave them a swabbing up and down, first couple of wipes on each flat blade in the connector came out black, I cleaned the sponge reapplied DeoxIT and then they were less black and after the third treatment they finally came away clean.

I then treated the connector with DeoxIT Shield which is recommended for use on contacts that have been cleaned so as to prevent future corrosion and tarnish when there is damp and fumes around.

I know from the appearance of copper circuit boards in a power supply I saw that had been in a closed in fan ventilated equipment room for six months in the middle of an open air bus station which sucked air into the equipment room from outside. When it failed we found the fumes from the vehicles had wrecked the copper traces. So over the years I suspect the vehicle exhaust fumes from other vehicles will not be good for the electrical connections. Hence my use of the Shield after cleaning.
Regards,
K-BIKE

Thanks for the details K! Sounds very similar to the process I used to clean up my airflow meter, but it sounds like I should look into getting some of the D100 cleaner to use prior to putting on the Gold protectant. I was using fine sand paper and cheap contact cleaner.

OG

Just scored some sponge wipes on E-bay. Thanks again K!

OG

If the bike starts ok when it is warm, do you use the choke when it is cold? The choke only comes into play when it is fully pushed forward on the handlbar leaver. If it springs back it is only in fast idle mode. Try holding the choke full on, while pressing the starter.

they call it a choke but it does nothing more than sets the idle higher by opening the throttle.
It is NOT a choke and does not act as one.
Ajays.

Right, it has two detented positions, both of which are simply fast idle positions. I reckon, because it's the same lever as on later model Airheads, which do have a 'choke', that it is BMW economising. I don't think 'Schneller Leerlauf' would look so good on that small space, either. Nor would 'Drosselklappe'. 'Choke' just fits the space better.
:joker:

Getting back to the Potentiometer, Bohumil wanted to know how to set it. This is the variable resistor mounted on the air flow meter and as Bert explains in his "trouble shooting starting" guide this varies the voltage between 2v and 12v as the vane moves open or closed. So setting it is not an option. Pins 5,7,8,9 on the injection computer plug are used to test it. But disconnect the tank electircs first. Apply 12v between pins5&8 and measure the output across pins 5&7 while moving then vane. The output voltage should vary smoothly between 2v and 12v. There is another factor which affects the output and that is the Air temperature sensor. ( another variable resistor/Potentiometer). See Berts write up there is a chart showing how resistance varies with temperature. Unfortunately it does not show resistance at anything below 20 deg c. But you can predict that it will be about 220-240 ohms for zero degrees.

Hi there, you can set the air flow meter, by changing the return spring stiffness, this is done adjusting the spiral spring with the teeth gear inside. For example if the spring is loose and the flap is opening to wide causing a rich mixture you can move a couple of notchs the spring and correct the relaxation due to age, as far as I know is a trial and error procesess, there are a few posts in the net regarding this subject for example http://skylands.ibmwr.org/tom/tech/l-jet-cal.html