Hello to all,

The saga of my non-starting K100 continues...

The story so far is:

I rode the back some time ago. It ran fine. The next time I tried it, no joy.

Since then I have inspected and cleaned/serviced/inspected various bits. Back together today and this is how it went:

The fuel pump runs, the bike starter motor engages, the engine fires for half a second and then dies - so back to square 1.

If the fuel pump is working fine, what can cause the engine to fire for a split second then die?

Is it likely to be: fuel injection control unit, CDI, relays? Mechanical (ie starter clutch system)????? Other?

Any contributions more than welcome as I am stumped by this.

Best to all,
Neal

Neal,

Any way to check if it's a lack of ignition or a lack of gas?

To check the ignition, I believe that you can use a strobe light. and see if the ignition dies after 1/2 second.
To check if the FI computer powers the injectors, you will have to install an LED in parallel with the fuel injectors.
This is the first step to troubleshoot. Find what stop working.

Was it raining the last time that you used it (No impossible as it never rain in the UK ) ? It was a recall on the 1984 ignition modules because they were not waterproof. If you open the ignition module cover, you should see if it's any mark of water. Reseal it after!

When the engine runs for 1/2 second, what is the maximum rpm? Does the engine reaches 900rpm?
- The EFI computer is pre-programmed to get maximum optimization during startup.
As long as the starter switch is depressed, the EFI computer will enrich the mixture air/fuel.
When the engine reaches 900rpm, the air vane position is fed to the EFI computer.
Have you tested the airflow meter?

If the engine stalls (no more signal from the Hall sensor), the Electronic ignition module will shut off the ground to the FI relay and to the coils. (This is to protect the output transistors and coils).
Does the FI relay shuts down?
Have you tested the Hall sensors? do you have a spare one on hand?

Good luck

Bert

There are basically two methods for fixing these sorts of puzzles the first often used by owners and bad mechanics is to throw parts at the bike until it fixes the problem - all at the owners cost of course. The good technicians diagnose and eliminate potential problems only replacing or fixing the faulty component/s.
What Bert has set down is a good logical process which will lead to answers about does the ignition die etc. I have been guilty in the past of changing components needlessly but the diagnostic approach is the way to go.
Regards,
K-BIKE

Hi,
Yes, I am convinced diagnostic is the better approach. Can't afford loads of new parts right now anyway!
I have read some other interesting posts on here where symptoms seem similar and will tackle the problem as best I can.
Anyway, I really appreciate the advice and knowledge shared via this forum!
Cheers,
Neal

A couple of thoughts for you,
Digital meters are good for absolute measurements of steady signals but very poor at spotting fluctuating voltages or currents especially if they are quick. I have a top of the line Fluke Digital and several genuine AVO meters.
Can I strongly suggest that all keep an eye out for AVO meters people are selling them because they think digital is better. I just bought an almost unused AVO 8 Mk 5 the absolute best AVO that was ever made from the point of serviceability into the future. I also bought a genuine well used 500 volt industrial Megger with the metal case and got the pair for the equivalent of 30 quid!

Back to normal mode, the really useful tools for electrical fault finding are the test light and the pointer type meter as these will tell you a lot about what is happening to a circuit such as a starter or brake light or a fuel injector or ignition coil primary. The meters are also easy to check for accuracy for resistance measurement since if you don't have access to standard resistors the 1% quality grade are cheap and form a very simple check of the meter resistance calibration prior to doing a check on say an air flow sensor. DC voltage can be calibrated from high quality watch battery type cells as they have a very well defined output voltage for their type when new.
Regards,
K-BIKE

Hi Neal,
Just checking how are you getting on with your problem?
Regards,
K-BIKE

Hi! Thanks for asking! I have not progressed as yet due to lack of time and because I feel a bit daunted by it frankly. I will have a go, using the diagnosis tips given by you and Bert and others. I will stay in touch with the forum as and when I have a go at it.
Cheers, N

Neal, have you got an AV meter? Can you measure between pin 10 and 13? This should give you the resistance of the coolingwater temp sensor. This sensor has two elements; one for the fan and overheating light, the other section is for the ECU to adjust the system for. If this signal is wrong (like 0 resistance) than the electronics think the bike is completely overheated and will stop the injection. So a short or too low resistance could lead to your problem.