My 1985 well used K100 is starting up and running perfectly and stopping dead It has just developed this problem after running perfectly for a year. It will not start, but the starter button runs the fuel pump.The starter will not turn over. The ignition lights stay on. After a few minutes it will start and run perfectly for a short time before dying. I suspect the computer, any suggestions welcome Sandy

Have you recently cleaned your electrical connectors? This could be all kinds of things, but as the bike takes all kinds of electrical signals to adjust the injection I'd start there. What you describe could be a result of a short in the cooling-water temperature sensor, resulting in the brain reacting as if the bike is completely overheated. What do you measure with an AV meter between pin 10 and 13 of the cable plug at the ECU (meter on resistance)?

The temp sensor checks out ok as do all the connections. The problem has deteriated for a once cut out a week ago to constantly dying yesterday to not start at all now. The ignition lights come on ,the starter button runs the fuel pump but the starter will not turn. The starter will work inderpendantly so it is not the starter. If it was the starter relay it should not die after starting and running. I think it must be a fault in the computer

Hi Sandy,
When you have the non start problem what do the spark plugs look like after a session of cranking are they wet with fuel?
Regards,
K-BIKE

When I have the problem, and now it is all the time ,the starter motor will not turn, only the fuel pump runs. The engine will not start if i similtaneously try ro start it and turn the starter over with an external battery jumped straight to the starter

Hi Sandy,
Sounds like the starter relay is not pulling in if the starter only runs when it is jumped to an external battery, are you jumping direct onto the starter or onto the existing battery? I would still like to know when you have been cranking and no start are the plugs wet or dry?
Regards,
K-BIKE

Hi, I had a seeminglike problem and it happen to be dirty starter brushes.
Best regards.
JAP

Hi K-Bike I was jumping directly to the starter with an external battery while pushing the start button The motor obviously turned over but did not fire. I have disconnected the temp sensor and the air flow meter and still got the same result.With everything connected up again I tried with the ECU plug out and it was the same whether connected or not. As I said before this was a minor problem last week and has progressed to this stage where it will not turn over I have not removed the plugs to see if they are wet since I can only turn the motor over with an external battery and if there was spark to the plugs it would fire. The starter circuit goes through the ECU and I think this must be the problem

Do you electricaly disconnect the starter from the bike, in orther to externaly jump it?.
Some of the bike´s circuits are grounded thru the starter and thats why dirty brushes are liable of many failures.
Best regards
JAP

Yes

Sorry I sent it incomplete
Best regards
JAP

Check the ground connection at the battery, a very similar thing happen to me, and the connector looked good, but was corroded inside.

Good luck,
Brian

So if you connect the booster battery in parallel with the bike battery it will not turn over when you push the button? If that is the case then the start relay is not pulling in.

Going through the basics given you have got the ignition switch on, the kill switch in the correct position, no sidestand switch and it still won't start.

Have you verified you are getting spark at the plugs?

Have you checked if the plugs are wet with fuel?

Until you can say yes to both of those we do not know if you have spark and fuel, either missing stops the bike firing. Even with the fuel pump running no signal to the injectors means no fuel gets injected and hence even with a spark and cranking - no run, please check you have spark and plugs wet with fuel (or not) and report what you find.
Regards,
K-BIKE

There is no spark and no fuel. I only used the external battery to see if the two problems were connected. They are ie cutting out and starter not turning over. I will try another ECU to see if it fixes the problem

Hi, Eventually located problem on undertank connector on right hand side. I cleaned the sockets and pins with a dremmel with a fine tip. Although the connector looked good it is very touchy since the two big pins and two small pins float individually and don't have pressure on them when connected in the way a relay does. Short of squashing the sockets with long nosed pliers or replacing the connectors with individual bullet connectors I can't see how to completely eliminate the problem. There are three of these type of connectors under the tank and I suspect that they will be a problem on all older K100's eventually. Still have an intermittant problem with the bike not allways starting in neutral. Does anyone know which undertank wire is the neutral gear wire?

Regards Sandy

If the bike doesn't detect neutral it will not start unless you pull the clutch.

The connection for the gear indicator (and neutral light) is located on the right side of the bike (where the connector for the speedo sensor is).
The problem is certainly the Gear position swich (TGIP switch).
Let's not reinvent the wheel and take advantage of a very good article written by Brian Curry:

Click here to get the page on theTGIP switch testing