Topic: 1975 cb750f will only start in neutral

[alec868]

bike only starts in neutral. nothing happens at all if in gear and clutch is in. seems like an issue with a switch.
 i know theres a neutral safety switch and a starter motor safety unit. i am wondering if the bike has some sort of cluch switch. i cant find one in the manual.
im wondering
1: is there a switch other than the starter motor safety unit.
2: how do i fix the problem

thank you

[Bankerdanny]

This same question popped up yesterday.

Yes, there is a safety switch that keeps you from using the electric start in gear without the clutch disengaged.

I'm not exactly sure where the switch is though. Check your manual for the location (download the manual from this site if you don't have it).

[Trav-i]

One of the switches is hidden in the control.  If you look near the lever pivot you will see two wires (sorry I forget the color) they connect in the headlight bucket, also pull the clutch lever in you sould see a very small plunger sticking out.  If you don't see the plunger then the switch is probably broken, also it was very common for the wires to break out of the switch too.

Hope some of this helps

Travis

P.S.  There is also a control box under the left cover, it should be red, you might want to look at it too.

[Toxic]

If you cross the two wires at the clutch you will effectively be bypassing the clutch safety switch, not always a good idea.  This little plunger style frequently breaks.

The starter motor safety switch can be bypassed as well.

[TwoTired]

This same question popped up yesterday.

From the same poster, too...
http://forums.sohc4.net/index.php?topic=90042.msg1008223#msg1008223

I suppose he'll just keep asking 'til he gets an answer he likes. 

[lucky]

The bike is a 1975CB750F.

I do not have a diagram for that bike but it is probably just like a CB750K.

The fact that the bike will not start in gear with the clutch pulled in is not really a problem.
All motorcycles used to be that way. You had to have the bike in neutral to engage the electric starter. That way if it WAS in gear it would not jump forward.

Any way at some point someone was at a stoplight and their poor running motorcycle stalled at a stoplight and they had to restart the motorcycle. So they had to put it in neutral and it took them so long that a car came up in back of them not paying attention and the motorcycle got hit. that is why they put in these switches so you can start the bike while it is in gear by just pulling in the clutch lever.

On the 1975 the system was comprised of a starter motor safety unit (grey box),
and a switch on the clutch lever. Also all the wiring had to be in place with the correct 1975 left and right handlebar switches to make it all work.


Then in 1977-78 models they got rid of the Starter Motor Safety unit thing and just have a diode in the circuit and the clutch lever switch. But the wiring is different.

You have to stick with either the 1975 wiring OR just eliminate the starter motor safety unit and not have that feature. OR re wire everything like a 1978.
And change both switches left and right.

If your bike runs and idles without stalling you will not need to worry about it.

[Xnavylfr]

you guys are so stuck on having every wire in the system for everything to work , you can remove 90% of all that UNNECESSARY wires and still have a operational system check here
http://www.hondachopper.com/garage/simple_wiring_diagram/simple_wiring_diagram.html
Most wires in the stock system are nothing more than a power lead and a ground return all the way back to the same plug-ins.
Most CB750s had a neutral safety switch in the gear area that prevented the starting without it being in neutral!

Xnavylfr(CHUCK)

[fatmatt650]

I thought that was how they were supposed to be. Only able to start in neutral. My ignition switch broke recently on my 77F and I found out the hard (stupid) way that this bypasses the safety feature. I hit the starter button while standing next to the bike (something I "never" do) and the bike lurched forward and fell over right there in the Safeway parking lot.
Can you kickstart the bike in gear w/ the clutch lever pulled in?

[Xnavylfr]

You can't start with the kicker if the clutch is in . The clutch dissengages from spinning the crank.
Yes the neutral safety switch was installed to prevent just what you did. I've seen lots of guys shut off their bikes with the rh grip switch then turn off the key. They come back later and try to start the bike to a point they run down the battery THEN relize the safety switch is OFF.DOH!

Most newer bikes have a safety in the kickstand, you can start the bike and get it warmed up , REV REV ready to go , kick it in gear and it dies WTF , oh the stand is still down!


Xnavylfr(CHUCK)

[Rigid]

Not a bad idea to have a functioning clutch and gear switch.  I touched the start button on my Harley and it lurched forward nearly knocking my wife off the back and me over on my side.  I caught the bike, luckily it didn't start and drive away without us. Some have the additional kickstand switch:

Clutch pulled - check
in neutral - check
kickstand up - check
OK, now it will crank.

[Gonzowerke]

The clutch switch on the lever is underneath, and held on with a tiny phillips screw. You can remove it and manually press it in to test it. If it is toast, then good luck finding another. What I did on my K8 was I hacksawed the clutch lever perch off of the switch pod, and used a clutch lever and perch from a '93 CBR600F3, that is separate from the pod. Then you just cut the switch wires and put some female crimp connectors on it, and it works fine with the switch from the 600.