OK so i have been riding my 75c for a little while and it runs ok but is still not the way it should be. I have found it has a lean idle condition and a rich running condition from about 2500 to a point where the engine starts to blubber and run lousy! The bike runs very well under a load and could not ask for a better running bike at that condition...but I am not sure if there is a vacuum leak or an air flow meter problem?

certainly sounds like you have described the condition for a leak condition well 8765k

there are 2 other places that would have a bearing on the rich running

1> the temp sensor in the stub in the hot water system ,,,if this was to have a higher resistance than normal it would run rich ....if you havent tested this before ....it might be a good thing to do you will find there is a graph of what it should read in the trouble / solutions info page .

this could be highly likely as i have seen a sensor pulled from a bike just recently with verry poor connection on the pins projecting from the sensor ....a clean up using a nail file of these pins would certainly have helped solve the issue on this bike ..... im not sure about the k75 but on the k100 it is a double ended sensor ...meaning the two pins are seperate connections to each sensor within the one unit (one controls the fan switching the other sends a signal to the injection control module ) the third wire is actually the earth/body of the threaded section of the sensor itself ....i am convinced that if you undo that sensor from the body (stub ) clean it up and reinstall it ,,,would be a good thing ....brass and aluminium are not the best elements to bond together...and im thinking it would be likely that there could be an electrolytic reaction betwen the 2 metals (making the path to ground high resistance ) ie: richer running .

2> the intake temp sensor (in the maf )

i recon it would be a good idea to undo the oil filler while the bike is idling and see if this changes the way it idles .

main suspect being the breather tube that sits near the back of the ignition coils and goes to the plenum (top of the throttle bodies ) if the above test fails to show any or little change in idle .

thirdy just a thought ....the thermostat in the water system is working ? do you have any way to measure if the temperature is changing to the right running temp ....if the thermostat was open all the time the bike would run cold for quite a while till it eventually heated up under a good load ...again running rich till it acheived operating temperature .



hope this helps

Further to the above (great!) info please understand that all connections in the system are important to ensure a correct resistance value is read by the ECU. This means that all electrical connections are important. These are the ones in the wires, but also the sensor to stub and the stub to frame contacts and then again the ground connections from the frame/engine back to the ECU.

Check the resistance when up to operating temperature and post the results that will enable you to determine if the resistance value is right. If by chance you were riding and see an airconditioning tech, those guys usually have an IR themometer.
Regards,
K-BIKE

Ok so I began to run through all of the things I have done to my 75c over the past years and checked the coolant sensor ground first by removing the plug from the sensor and plugging in another known good sensor( I did not remove the old one ). started the bike without grounding the body of the sensor and the bike ran exceptionally well as long as i did not ground the body. As soon as I ground the body the engine starts to run rough and will not rev without coaxing the throttle. I tried to start again this way another time and now it it flooded...???

main suspect being the breather tube that sits near the back of the
ignition coils and goes to the plenum (top of the throttle bodies ) if
the above test fails to show any or little change in idle.

hi charlie, i've done the oil filler test and the engine slow downs a lot. if cold it will stop. i also found a dislodged rubber tube under the petrol tank which i cannot find where it is attached to i think something is wrong here. any ideas?

the other thing that comes to mind .....is that all this stuff may just be corrrect ...and infact the springing / metering pot in the maf may well be "out of wack " meaning, for a given flow the resistence values sent to the injection control might be suspect ...



from memory bert did some research into this and included some resistance values etc in the "efi trouble shooting thread" on the portal page .......i suggest that you take measurements and compare results from all these critical subsystems (temp sensor , maf air sensor , maf ,etc ) it sure would be handy to have it all logged to make a comparison to what works and what you have ....no ?

btw a good place to measure the water temp sensor is pin 10 of the injection control (making sure that is has a good earth )) all the others could be measured there as well ...given that you look up the appropriate pinouts

given that you have different/unpredictable results so far ...i wonder if there is something not quite right lurking in the main loom ...possibly a faulty connector ...wire between source and injector control ...





vic ...that sounds about right ...the engine should die / run rough....the lines from the under tank may have connected to the tank breather etc different models have different ways of doing this it apears .....like on my 85-86 model i have a little cup on the frame that collects the run off ...where as some others dont ?