Topic: neutral light stays on every gear 1978 cb750f (3?)

[sohcphreek]

I have never removed a neutral switch before and would like some input from a experienced sohc pro! Does the oil leak out? can the switch be cleaned or should i have a new 1 in hand?  thanks for any help. sohcphreek

[Jonesy]

Before you pull the switch, check the wire. The switch completes the ground side of the neutral light circuit, so if the wire going to the switch is chafed or pinched anywhere, the light will come on.

If the wire checks out OK, the switch might not be fully seated in the bottom of the crankcase. This can happen if the O-ring on the switch is the wrong size. If you have to pull the switch, a few drops of oil might come out, but nothing major. Some people have been able to take the switch apart and clean it.

[sohcphreek]

I think wires are fine and it's never been apart. It just started this on my last ride. all of a sudden the shifts didn't seem as crisp and clean as they have been for the last 15 years. I changed the oil and filter but this didn't help either. sohcphreek

[spitfire]

Had problems with the neutral light on my 76 750F1, staying on 2 years after I bought the bike (1978), I changed the switch and it still would not go out, so I taped over the light on the console.
When I removed the engine last year at the start of the rebuild I found the real problem, the cable to the switch was grounding out under the engine where the cable had chafed.
The light started playing up again recently so I removed the switch and tested it on the bench, it was fine, but I had put the retaining clip on the wrong way and the switch was not seated properly, with the clip in the correct position all is well.
No oil came out, if however your bike has been sitting for a while there may be some oil in your bottom end and you may get some leakage.

Cheers

Den

[sohcphreek]

Thanks for the info. I should not assume the the wires are good!! you know what they say about assuming!
Going to the garage now to trace the wires  oh theres a fridge full of sierra nevada ale. i'll get through this!
thanks again

[Steve F]

Thanks for the info. I should not assume the the wires are good!! you know what they say about assuming!
Going to the garage now to trace the wires  oh theres a fridge full of sierra nevada ale. i'll get through this!
thanks again

Before you make it any harder than it needs to be, just disconnect the wire from the switch, and let it hang while the key is on.  If the light stays lit, THEN start tracing back through the circuit.  If the light goes out, it's the switch.

[Canada]

I was also having the problem too. I removed the switch and it tested fine. I was having the problem where the light would be on all the time but when in neutral it would get a hair brighter. The best that I can tell is that the little ball that activates the light is partially pushed in due to the the "little wheely thing" that it fits into when the transmission is in neutral. I could be way off base with this theory! When not in neutral the ball stay partially depressed so the light stays on. Or is it the other way around? I can't remember! I was lucky and it has seemed to work itself out. Not sure if this helps???

[KB02]

What if the switch doesn't want to seat all the way in? I'm having the same problem. When I had the engine out and put the switch back in, it didn't want to seat all the way in. I was afraid (rightly so?) to pound on it with any kid of hammer.

[jtb]

Have someone push on the switch, while you shift up and down through the gears.  All of a sudden it will seat correctly.  If it is not all of the way in, the light will stay on all the time.  (I knew a girl like that... )

[Impi]

jtb... I am frustrated with the same issue but reading your last comment (Knew a girl like that) and it just turned my frustration into a really good laugh and ready to fight it some more!

[madmtnmotors]

Test the diode (not the rectifier) before replacing anything. I've replaced three of them lately. A bad diode will "backfeed" and turn on the neutral light.

[70CB750]

Most of the Neutral lights problems are related to switch seating - like wrong o-ring size.

[madmtnmotors]

Most of the Neutral lights problems are related to switch seating - like wrong o-ring size.

Except that this has suddenly appeared after 15 years without ever having removed the switch...

I think wires are fine and it's never been apart. It just started this on my last ride. all of a sudden the shifts didn't seem as crisp and clean as they have been for the last 15 years. I changed the oil and filter but this didn't help either. sohcphreek

Testing the diode doesn't cost any money and can be done with a continuity tester in about 30 seconds to rule it out. 

[flybox1]

Thanks for the info. I should not assume the the wires are good!! you know what they say about assuming!
Going to the garage now to trace the wires  oh theres a fridge full of sierra nevada ale. i'll get through this!
thanks again

Before you make it any harder than it needs to be, just disconnect the wire from the switch, and let it hang while the key is on.  If the light stays lit, THEN start tracing back through the circuit.  If the light goes out, it's the switch.

^^ this