Topic: starter motor safety unit bypass

[jscro73]

guys,

how can i bypass the starter motor safety unit on my 73 cb750?
i read some of the other posts, but none really said anything about actually removing the unit and clutch switch and being able to successfully start the bike.
thanks,
Jason

[Spanner 1]

If you unplug the SSU and remove it you can by-pass it's function by jumping the solid Green wire to the Dark Green/Red wire( there is also a light green/red ). That's it, your done........the starter will now spin whether your in gear or N or clutch is pulled or not...  N light will still work when in N 'tho...........

[Bill/BentON Racing]

More info in reply by Hondaman today in post for CB750 RH switch compatibility.Bill

[MJL]

Since he clutch lever switch was broken on my 750, I followed those wires into the headlight bucket and basically plugged them into each other. Just don't hit the button without double checking first or being on the bike.

[Spanner 1]

Sorry but Hondaman's post in the thread referenced by ' bellcow ' is wrong......a black +12V would never go to a Green-with-red-tracer as it is a switched ground...i.e. it is a ground wire when in Neutral or some other switched condition..... sorry ,but my post of 1 jumper between two wires is correct if you really want to do away with the safety switch ( no start in gear or no start without clutch pulled if in gear, start as usual in N , starter engages any time you hit the button if by-passed )

[HondaMan]

Sorry but Hondaman's post in the thread referenced by ' bellcow ' is wrong......a black +12V would never go to a Green-with-red-tracer as it is a switched ground...i.e. it is a ground wire when in Neutral or some other switched condition..... sorry ,but my post of 1 jumper between two wires is correct if you really want to do away with the safety switch ( no start in gear or no start without clutch pulled if in gear, start as usual in N , starter engages any time you hit the button if by-passed )

You missed something, there: the GREEN-RED wire I'm referring to is about 2" long, and it is attached to the Starter solenoid. It's not tied to the harness's GREEN-RED wire at all.

Because, if it was, you'd be absolutely right... 

[Spanner 1]

With respect, the original posters question was concerning K3 wiring( actually up to K5 ) where the green/red was a switched ground...wait, no, K6,7,8 F1,F2, still a switched ground...even K0 ( light green/red )......green/red on the solenoid is also a switched ground..i.e. waiting for the trans. to be in N or the clutch to be pulled to send ground to the solenoid.....

[the technological J]

With respect, the original posters question was concerning K3 wiring( actually up to K5 ) where the green/red was a switched ground...wait, no, K6,7,8 F1,F2, still a switched ground...even K0 ( light green/red )......green/red on the solenoid is also a switched ground..i.e. waiting for the trans. to be in N or the clutch to be pulled to send ground to the solenoid.....

you know that fine line between genious and insanity...... ur there guys..ur there

[jscro73]

bellcow, i may just bring it over to you, if you're willing to take a look at it. i live in hiram. i'm getting frustrated with this bike. before barber, i was getting no spark anywhere (coils and points), came back from barber, found out that i didnt put the insulator between the power wires and the grounds @ the points. then, drained my battery, and when i recharged my battery, the solenoid just clicked. then i put a new set of handle bars on the bike. Now, the starter button wont work, but i've got spark @ the points, but i think my starter safety unit is bad, so i wanted to bypass the whole thing for the time being. I dont think the switch is bad. i ran several tests on the wires to make sure i didnt cut anything, and i have continuity. i'm gonna test the switch tonight.

jason

[lucky]

If you unplug the SSU and remove it you can by-pass it's function by jumping the solid Green wire to the Dark Green/Red wire( there is also a light green/red ). That's it, your done........the starter will now spin whether your in gear or N or clutch is pulled or not...  N light will still work when in N 'tho...........

Solid Green wire from WHERE? (the harness- safety unit plug in?)
"to the Dark Green/Red wire (where?) On the safety unit harness- plug in?

Or do you mean on the solenoid itself?

Not clear at all.
Can you tell us where these two wires are at that you are jumping? Thanks.

[Toxic]

When you unplug  the SSU you are left with a red multi pin connector, you make a jumper wire to go from the green/red to the solid green.
If you don't have the SSU plugged into you harness use you wiring diagram to find this red connector.
Let me know if you want a pic.

[the technological J]

hope he got it figured out by now...... 2 years late!

[Spanner 1]

Toxic must be off his meds again 

[lucky]

If you unplug the SSU and remove it you can by-pass it's function by jumping the solid Green wire to the Dark Green/Red wire( there is also a light green/red ). That's it, your done........the starter will now spin whether your in gear or N or clutch is pulled or not...  N light will still work when in N 'tho...........

Solid green wire from where ? To Dark green/red wire where?
Do you mean jumping the DG wire to green wire on the plug that the starter motor safety unit was plugged into?
So what did all of this stuff in the Starter motor safety unit do?

Makes me think some electronic genius wasted a lot of time making this"safety unit"
And now they just use a clutch switch diode with clutch switch lever switch? I wish I understood all of it better.

[Toxic]

Here Ya go Lucky.
Here is a pic of what Spanner is describing above.





This red plug is where my SSU was plugged into.  Don't know if yours is red or white but check the wiring diagram for your bike.

[lucky]

The picture makes it very clear which wires are being jumped.
I am restoring a bike now and have a new wiring harness and I wanted to make it all a 1975 wiring plan but right handlebar switches are very hard to find.
I may have to do away with the starter motor safety switch after all.

You cannot buy them anymore so I might as well get rid of it.

Thanks for you help and patience.

BTW...What YEAR CB750 did you do this jumper wire modification on? Thanks.

[HondaMan]

The picture makes it very clear which wires are being jumped.
I am restoring a bike now and have a new wiring harness and I wanted to make it all a 1975 wiring plan but right handlebar switches are very hard to find.
I may have to do away with the starter motor safety switch after all.

You cannot buy them anymore so I might as well get rid of it.

Thanks for you help and patience.

BTW...What YEAR CB750 did you do this jumper wire modification on? Thanks.

K3 and later (1973 onward.

Before that, ALL bikes let you hit the starter in gear if you wanted to: I still make all the bikes I build that way so it won't strand someone in a busy intersection on a hot day when the ethanol in their carbs is boiling and the bike stumbles and quits 20 feet into the intersection after a red light...You just hit the button and fireit back up instead of looking for Neutral or having to pull in the clutch (if your clutch switch still works).

Laws don't make people smarter, people do...

[1080]

lucky

In the Honda 750 manual there is a schematic of the safety unit, but there is no values to the parts it requires to make one. With your unit, all the compounding removed, a person with good electronic background could repair yours.

I think the lamp filament breaks & it renders the unit useless?

[nwrocker]

When I tried this the 15 amp main fuse blew.  Dark green with red stripe to green.  The guy who had the bike before me had hot wired a switch to the two posts of the solenoid to start the bike. I am trying to figure out if I have a problem in the starter switch, neutral safety switch or in the solenoid.   Could the starter solenoid be shorted?

[lucky]

When you unplug  the SSU you are left with a red multi pin connector, you make a jumper wire to go from the green/red to the solid green.
If you don't have the SSU plugged into you harness use you wiring diagram to find this red connector.
Let me know if you want a pic.

VERY CLEAR  Thanks!! Works perfect.
I just made up a little 3 inch jumper wire with terminals.

[Blue2swing]

I know this is an old thread but I feel this is the best place to place my question.

Would it be possible to jump the "light-green/red" wire with the "Dark-green/red" wire if a diode was soldered in the "jump wire" allowing current to flow from the "light-green/red" wire to the "Dark-green/red" wire only? To clarify, the diode would allow current to flow from the neutral switch to the clutch-switch wire that feeds the engine start button only, and not the other way around.

This way we can remove the starter safety unit, but still only allow the bike to start when the bike is in neutral OR the clutch lever is being squeezed.

Thanks in advance, and I hope the wording of my question isn't too confusing.

[madmtnmotors]

I know this is an old thread but I feel this is the best place to place my question.

Would it be possible to jump the "light-green/red" wire with the "Dark-green/red" wire if a diode was soldered in the "jump wire" allowing current to flow from the "light-green/red" wire to the "Dark-green/red" wire only? To clarify, the diode would allow current to flow from the neutral switch to the clutch-switch wire that feeds the engine start button only, and not the other way around.

This way we can remove the starter safety unit, but still only allow the bike to start when the bike is in neutral OR the clutch lever is being squeezed.

Thanks in advance, and I hope the wording of my question isn't too confusing.

It sounds like you are describing the later model configuration. The 77/78 CB750's used a diode exactly the way you describe. I recently had to replace the diode in my K8 after chasing my tail trying to figure out why the neutral light would not go off. Look at the wiring diagrams for the 77/78 models. I'm not sure if the early harness has everything you would need to make the conversion, but it sounds good in theory.

[rotortiller]

I got the same T-shirt LOL!

I recently had to replace the diode in my K8 after chasing my tail trying to figure out why the neutral light would not go off.

[Blue2swing]

It sounds like you are describing the later model configuration. The 77/78 CB750's used a diode exactly the way you describe. I recently had to replace the diode in my K8 after chasing my tail trying to figure out why the neutral light would not go off. Look at the wiring diagrams for the 77/78 models. I'm not sure if the early harness has everything you would need to make the conversion, but it sounds good in theory.

I'm working on a 75 K5, but I did get the idea after looking at a wiring diagram for an older cb750 and then seeing the "Saftey unit's" internal wiring diagram (that is also posted on this thread). I'm making a wiring harness from scratch so I can simplify the who system while installing a M-Unit and converting all the lights to LED's. I have too attach a diode to the turn signal indicater led since I'm only using one light to represent both turn signals. I think if I purchas a second diode too install on the neutral-switch wire and jump it onto the clutch-switch wire I should be able to replicate the action of the "Saftey Unit" without having to continue too use the big ugly box.

I'll give it a shot and report back. But it may take a while as I don't think I'll be completing the harness within the next 2 months.

Here's the diode I plan too use
http://www.dimecitycycles.com/inline-diode-kit.html

[Pat_at_APE]

What are the specs for the diode?   I've got the same issue on my 77.....

Thanks,
Pat