Author Topic: THE DIODE - why is it needed?  (Read 14814 times)

0 Members and 4 Guests are viewing this topic.

Offline HedNut

  • Underwater Basket Weaving
  • Expert
  • ****
  • Posts: 844
  • CB750...A Two-wheeled hellcat from Planet Kickass
THE DIODE - why is it needed?
« on: November 12, 2009, 12:01:43 pm »
I am re-wiring my bike....cutting out what I can to simplify the deal.  And have a question...

THE stand alone DIODE... (circled in red in the 77-78' schematic below)

Why is it needed??

If anybody knows...please enlighten me!

GREATLY APPRECIATED ALL!

PS....It's connected to the starter switch, neutral switch, clutch switch and neutral light.
The K1's don't have them (I also attached a K1 Schematic)....they also don't have a clutch switch.....soooo....could I lose the clutch switch and diode...and keep the neutral indicator? (I could aslo live without the neutral light) If so how?

Offline Raul CB750K1

  • Old Timer
  • ******
  • Posts: 3,881
Re: THE DIODE - why is it needed?
« Reply #1 on: November 12, 2009, 12:36:03 pm »
What is the problem with the diode?

You may know that a diode only allows current through it in one direction. In electrical -not electronic- circuits, diodes are mainly used to impede back-current. It is difficult to explain but I will try: say that you want a buzzer when either of blinkers go on. You could connect the buzzer to ground and then to the left blinker. It would buzz ehen the left blinker is on. What about the right one? Simple, go ahead and connect the buzzer ALSO to the right blinker. Then the buzzer will buzz when either of the blinkers lit.

But the undesired effect is that you have put together both blinkers, then, when either one is lit, it will lit the other one. To avoid this you can use two diodes. When the left one goes one, current will go to the diode and to the buzzer, then via the cable to the right one but it will find a diode in reverse, thus it won't make the right blinker lit.


As I say, a diode is fairly cheap, you can put any one and keep the electrics as they were. I have bikes with clutch switch and without, sometimes I push the starter with the clutch engaged and the bike pushes forward, but never had any accident. I mean, you can't live without it, but it won't hurt you and the price of a diode is cheap insurance. More than that, I appreciate the sidestand switch, a few times I have run away with the sidestand released.

Offline BobbyR

  • Really Old Timer ...
  • *******
  • Posts: 12,367
  • Proud Owner of the Babe Thread & Dirty Old Man
Re: THE DIODE - why is it needed?
« Reply #2 on: November 12, 2009, 12:41:33 pm »
I have bikes with clutch switch and without, sometimes I push the starter with the clutch engaged and the bike pushes forward, but never had any accident. I mean, you can't live without it, but it won't hurt you and the price of a diode is cheap insurance. More than that, I appreciate the sidestand switch, a few times I have run away with the sidestand released.
This of course will only happen in front of pretty girls or guys who will make fun of you. Never fails. ;D ;D
Dedicated to Sgt. Howard Bruckner 1950 - 1969. KIA LONG KHANH.

But we were boys, and boys will be boys, and so they will. To us, everything was dangerous, but what of that? Had we not been made to live forever?

Offline CB750F2

  • Hot Shot
  • ***
  • Posts: 645
  • Pat's first Honda 750 F2
Re: THE DIODE - why is it needed?
« Reply #3 on: November 12, 2009, 02:40:07 pm »
Hednut, the diode is required to give proper indication of the neutral light. If you replaced the diode with a short length of wire the neutral light will light up every time the clutch was pulled in - when changing gears for example. If the diode was removed without replacing with the short length of wire the neutral light will still work but the starter would only work when the clutch was pulled in. I suggest that you or someone that can draw a basic electrical diagram draw up that part of the circuit. If you do this you will find it much easier to follow than trying to follow the wires in the complete diagram that you have shown. The K1 system uses a neutral switch and light for indication purposes only. There is no interlocking with the starter motor. Hope this helps, Pat
Regards
Pat from Australia

Offline Spanner 1

  • Old Timer
  • ******
  • Posts: 4,092
  • CB 750 K0 ( always thought it was a K1!) + CB750K8
Re: THE DIODE - why is it needed?
« Reply #4 on: November 12, 2009, 05:47:38 pm »
One day I went to start my K1 in strong sunlight and I thought the bike was in N ( couldn't see the N light clearly ) . First touch of the start button and the bike jumped forward off the side-stand and dropped on it's left side....... Diodes are good... !!
If your sure it's a carb problem; it's ignition,
If your sure it's an ignition problem; it's carbs....

Offline HedNut

  • Underwater Basket Weaving
  • Expert
  • ****
  • Posts: 844
  • CB750...A Two-wheeled hellcat from Planet Kickass
Re: THE DIODE - why is it needed?
« Reply #5 on: November 13, 2009, 04:45:01 am »
Sounds like diodes are a little bit of alright.

  Thanks a lot guys! You have enlightened me, and I understand it now.  I am honoured to be in the precence of such experience and smarts on this board.  Truley appreciated fellas!
 And when I get a moment...I will draw up a schematic of the diode circuit alone...for some self clairity....and post it here.

Cheers!!
AND THANK YOU ALL

Offline cafe2be

  • Hot Shot
  • ***
  • Posts: 564
Re: THE DIODE - why is it needed?
« Reply #6 on: November 13, 2009, 10:13:32 am »
I am running a diode-LESS bike. Its not part of my wiring harness and have not had any problems.

Offline CB750F2

  • Hot Shot
  • ***
  • Posts: 645
  • Pat's first Honda 750 F2
Re: THE DIODE - why is it needed?
« Reply #7 on: November 13, 2009, 01:36:23 pm »
If you were to disconnect the clutch switch and replace the diode with a short length of wire the circuit will work fine but you will loose the ability to start the bike when not in neutral by pulling the clutch lever. If this is OK with you then go for it. Pat
Regards
Pat from Australia

Offline mystic_1

  • Really Old Timer ...
  • *******
  • Posts: 6,071
  • 1970 CB750K
Re: THE DIODE - why is it needed?
« Reply #8 on: November 13, 2009, 04:53:21 pm »

Here ya go.


mystic_1
"A ship in harbor is safe, but that is not what ships are built for."
- John Augustus Shedd

My build thread:  http://forums.sohc4.net/index.php?topic=68952.0

Offline mystic_1

  • Really Old Timer ...
  • *******
  • Posts: 6,071
  • 1970 CB750K
Re: THE DIODE - why is it needed?
« Reply #9 on: November 13, 2009, 05:14:51 pm »
Or, to put it differently....




mystic_1
"A ship in harbor is safe, but that is not what ships are built for."
- John Augustus Shedd

My build thread:  http://forums.sohc4.net/index.php?topic=68952.0

Offline mystic_1

  • Really Old Timer ...
  • *******
  • Posts: 6,071
  • 1970 CB750K
Re: THE DIODE - why is it needed?
« Reply #10 on: November 14, 2009, 05:56:08 am »
Easier to read:

mystic_1
"A ship in harbor is safe, but that is not what ships are built for."
- John Augustus Shedd

My build thread:  http://forums.sohc4.net/index.php?topic=68952.0

Offline HedNut

  • Underwater Basket Weaving
  • Expert
  • ****
  • Posts: 844
  • CB750...A Two-wheeled hellcat from Planet Kickass
Re: THE DIODE - why is it needed?
« Reply #11 on: November 16, 2009, 06:49:51 am »
Very Cool Mystic!! Thanks!

Offline mystic_1

  • Really Old Timer ...
  • *******
  • Posts: 6,071
  • 1970 CB750K
Re: THE DIODE - why is it needed?
« Reply #12 on: November 16, 2009, 08:49:53 am »
No worries :)

BTW for those unfamiliar, current can flow through the diode in the direction of the arrow but cannot flow in a direction opposite the arrow.

Power enters via the key switch, through the start button and then the solenoid, and is grounded through either the neutral switch or the clutch switch.  The diode makes it so that only the neutral switch can light the indicator light (current cannot flow through the light and into the neutral switch).


hth

mystic_1
« Last Edit: November 16, 2009, 08:51:56 am by mystic_1 »
"A ship in harbor is safe, but that is not what ships are built for."
- John Augustus Shedd

My build thread:  http://forums.sohc4.net/index.php?topic=68952.0