Hi Brainiacs...

As with most things in life ...we seek out the wizened in search of answers.

My problem is the K is sick, she will fire up on the button but then dies after a few seconds. It seems to be too sudden to be a fuel issue and therefore most likely an electrical one.
I have been using the troubleshooting guide, and am at the hall sensor test with the 12v LED

My question is...what would cause the LED to overheat and burn out? obviously a short but where?

Any and all input greatly appreciated

Ogri

An LED will only burn out with too much voltage. There is no such thing as a 12 volt LED as they are all between 2,2 and 4 volts or so. A 12 volt one will be a normal LED with a resistor in the wire to it.

Apologies, I meant a normal low voltage LED...I did a diode check with multimeter on the sensor and it shows .9 for both ...

leds are rated for a certain current for continuous operation (across the led junction ) with out damage . they will draw huge currents without this and being put straight across 12 volts .

leds that are rated for a voltage have the correct current limiting resistor in place (series) for that application and the led parameters

most commonly ...typical currents through leds are about 20 milliamps  so if you bought just any old led you would have to limit the current to it if you want it to survive longer than a few seconds .
560 or 680 ohm resistor is suitable and safe for most leds in 12 volt applications.



the other thing that you have to remember is that the sensor will only switch a small current safely before damage to the device WILL happen .... so when folks say use a led ...keep currents small before damage will occur to everything in the circuit

In the short time that the bike fires do you get fuel going back into the tank?

ungaas wrote:In the short time that the bike fires do you get fuel going back into the tank?

I can hear the fuel pump prior to starting, but it stops when the engine stops and doesn't start up again...

Hi Ogri, I didn't know we had a K back the west!!  I doubt it is the Hall sensor but others on here will know more. I have a K engine here near Tralee and have some engine and electrical bits, Darren also in Tralee has a K and some spares too.
If you come across the hill some day give me a call. Philip

If the engine doesn't fire the fuel pump will run for 1.5 seconds after the starter button is released and it sounds to me like that is what is happening when the engine has actually started.
Your hall sensors are putting out the signal as the engine is starting but not continuing to run so the fuel pump isnt getting the signal to keep running.
So either the ECU is faulty or the Yellow/Red wire from terminal 1 on the ECU to terminal 8 on the ICU is open circuit. Check you have continuity on that wire and if that is OK reseat the plug on the ECU and ICU and then if that fails try to borrow an ECU and try that. The yellow/red wire goes through a 4 pin connector so that may need some attention.

RicK G wrote:If the engine doesn't fire the fuel pump will run for 1.5 seconds after the starter button is released and it sounds to me like that is what is happening when the engine has actually started.
Your hall sensors are putting out the signal as the engine is starting but not continuing to run so the fuel pump isnt getting the signal to keep running.
So either the ECU is faulty or the Yellow/Red wire from terminal 1 on the ECU to terminal 8 on the ICU is open circuit. Check you have continuity on that wire and if that is OK reseat the plug on the ECU and ICU and then if that fails try to borrow an ECU and try that.  The yellow/red wire goes through a 4 pin connector so that may need some attention.

I checked that yellow/red wire end to end and connector and all good...and all seated properly....

Is there any chance its related to the clocks? The rev counter was jumpy on smooth tickover, and there was a small bit of condensation inside them, I took them apart but didn't see anything amiss on the PCB....

Testing the hall sensors is the next logical step but seeing it fires initially it is unlikely that is where the problem is.
I would be trying to borrow an ECU and ICU then swap them around.

RicK G wrote:Testing the hall sensors is the next logical step but seeing it fires initially it is unlikely that is where the problem is.
I would be trying to borrow an ECU and ICU then swap them around.

Hover has graciously offered to do just that....preferably sooner than later as I miss my ol K....

Case closed....traced frayed wiring within the loom going into the starter relay. Running sweet and flying as a brick should. Took her over the Connor pass and around Slea Head yesterday in sweltering sunshine.

Thanks for all the replies and offer of assistance.

I'd like to know more. Was the wiring worn through against a sharp edge and broken?.....or shorted?
Are there any photos of the problem area?

I'd also like to understand more from the electrical guru's here what was actually occurring? Was the bike running during start sequence but stopped as soon as the load shed relay closed????
Just trying to learn more about how things work.

Congratulations on getting it fixed and especially, THANK YOU for actually posting the "Solved" report.

Regards, Ibj...

Alas I didn't take pics, but it was under the wiring box there is a rubber grommet that was missing and had thru vibration, partially cut thru a couple wires ....they hadn't melted much and a quick snip, solder and heat shrink they were sorted.

a good result ogri