it is a UK bike yes. it's a 2001 without a hiss system. pulse gen,stator,ICU,plugs,starter,fuses,battery,all external wiring and parts,loom wiring,coils,HT leads,the whole damn thing has been tested several times by several different people, all giving close to or perfect readings as per the workshop manual. and it has all come down to this diode and the dreaded "pink wire" problem. the loom has the lights deleted along with the clutch and side stand switch. the deletes are done correctly and the loom has 12v where it needs it and not where it doesn't. I have used all sorts of zener diodes and resistors and can't get it down to 9v on the pink wire no matter what I use in what order and in any direction.........trust me......I've tried a **** tone of them 🤣
my original question was really, as soon as I turn the key on (not the original key, this is a custom build,hence the diode needed) should it be 9v? or, can it be say 10.57 but change to 9v when you turn the bike over on the starter button?

I think hiss came in on 2002 bikes...?
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I now have these......what one do I use ??

 

Measure output of diode before connecting pink wire to it.

You’ve got some other power-wire connected to pink wire downstream somewhere. Trace pink wire end-to-end and verify it doesn’t touch any other wire.

Also your battery is dead. Should be >13,0v with everything off. And not drop below 11,0v when cranking. Otherwise there’s not enough power to run ECU. Might as well remove ECU from bike and try to start it

BTW - other guy that said diode is regulator and always outputs 9v regardless of input is also an idiot. You’ve been struggling because you’re getting your info from idiots! Zener diode drops fixed amount of voltage from input, no matter what that is. So a 3,9v diode drops 3,9v from input and sends that to output. Varying input voltages will resulting in different outputs:

input 13,5v - 3,9 = 9.6v output
input 13,0v - 3,9 = 9,1v output
input 12,5v - 3,9 = 8,6v output

Most likely diode is fried from heat of soldering and having power applied to both sides. Test diode 1st before using, you’ve probably been using dead diode all this time. Make sure it’s good before using by testing it by itself. Pick new 3,9v diode from your kit and test:

1. Measure battery power, volts=??

2. Touch diode stripe end to battery +pos terminal. Measure power at other end, volts=???

3. Touch diode other end to battery +pos terminal. Measure power at stripe end, volts=???


We’ll also need to test for power at all components, grounds, trigger wires and proper relay operation. But one at time, diode 1st.

Also looks like harness is quite hacked up. We’ll need to trace and measure every single wire end-to-end and verify each one is according to manual. Or get brsnd-new factory OEM harness from authorised Honds dealer. Who knows what kind of mods PO has done.

 

You’ve got some other power-wire connected to pink wire downstream somewhere. Trace pink wire end-to-end and verify it doesn’t touch any other wire.
there is no other wire connected to the pink wire. it goes directly to the ICU and is wired in to the switch live. it's here that it should drop to 9v from 12v......

Also your battery is dead. Should be >13,0v with everything off. And not drop below 11,0v when cranking. Otherwise there’s not enough power to run ECU. Might as well remove ECU from bike and try to start it
battery is pretty new and holds just over 13v when fully charged but I will remove one from another bike and try it anyway.



Most likely diode is fried from heat of soldering and having power applied to both sides. Test diode 1st before using, you’ve probably been using dead diode all this time. Make sure it’s good before using by testing it by itself. Pick new 3,9v diode from your kit and test:
that sounds perfectly feasible. are you able to "twist" them on to the loom wires for testing purposes or should they always be soldered in to get a true reading?

thank you for your time!!

 

HISS was introduced earlier than that.
What’s part# on ICU?
Do you have HISS light on clocks?
Does your key work in ignition, tank cap, helmet/seat lock?

 

You’re welcome!

No, test diode by itself by touching one end directly to battery and measuring other end. No wires, no soldering needed.


Stop swapping stuff around without measuring. Will replacing air in your tyres help bike start? How about replacing tyres themselves? What if you get new chain & wheels, will that help bike start?

If you get different battery, it could be worse than yours and will also need testing to verify it’s good. Might as well test one on bike:

1. Measure battery power with everything OFF, volts = ??

2. Meausre battery power with key ON, volts = ??

3. Measure battery power during cranking, volts = ??


Key ON, stop-switch=RUN,

4. measure power at each ignition-coil’s blk/wht wire, volts1=??, volts2=??

5. Measure power at ICU’s blk/wht wire, volts=???

6. Measure resistance between ICU connector lt.grn wire and chassis-ground, ohms=???

7. Measure resistance between ICU connector grn/wht wire and chassis-ground, ohms=???