Topic: Can clutch adjust=no neutral light?!

[theofam]

BB, reply #12 - '78 750K.

Phil71, I figured replacing the bulb was unnecessary since the voltmeter already showed 12.3V on the wire coming from the bulb.  Voltage from bulb=good bulb.  To your point, I didn't want us blowing any more time on this in case my understanding was incorrect.  I swapped the good oil pressure bulb with the existing neutral light bulb and still, no light.  I'm trying to avoid the costly process of simply swapping components until it works.  I'd rather use my multimeter to tell me where the problem is.

Based on input from you guys, I'm pretty sure at this point it's either the diode or a loose/bad connection in the harness.  So, I'll be able to jump on this Tuesday.  I'll first test the diode.  If it's good, I'll start unwrapping the harness to see where that light green/red wire is problematic.

Take care!

[DarcyCB400F]

I am curious if you have taken the bike for a ride since adjusting the clutch? Can you find neutral without the light? Does if flash when you shift to second from 1st?

[Oddjob]

Damn I should have thought of this before but it's been a few years since I've had to repair one of these and it slipped my mind.

Grounding out the phillips screw on the end of the selector drum may not highlight the problem. The neutral light switch works by grounding the neutral wire through the switch and onto the oval piece screwed onto the selector drum. This small oval piece is made of a sort of bakolite or hard plastic, it has a brass strip running through it and around the screw hole, the strip is right on the upper edge of the oval section. It's this strip which connects with the neutral light switch, as soon as you select neutral the strip connects, however the inside of the chain case gets rather grubby/greasy and sometimes the strip gets covered in gunk OR the very tip of the neutral switch where it would connect to the strip breaks off or bends away. As the switch can no longer ground you get no light.
Pull off the green/red wire from the switch, it should be a male connector and just push into the switch so should come off very easily. Hold this wire against the engine and if it lights the switch or strip need cleaning or some slight attention. Extremely easy to do this so I'd do this first as I'm 99% sure the problem lies there.

[theofam]

Darcy, I can't ride it yet. Still piecing it together.

Oddball, I had checked the switch and had power to it, so I decided it was the diode or wiring harness. The diode was OK, so I took off the wiring harness last night.

There was a spot on the harness that was chafed, but I unwrapped the entire harness to check the entire neutral light wiring. The wire looked great front to back, but I decided to cut and solder the wire where the wrap had been chafed. That fixed it!  I have a neutral light again!!

So, it was a bad wire to the headlight bucket . . . CASE CLOSED . . . WOOHOO!

[DarcyCB400F]

Congratulations! wiring gremlins are always nasty business!

[Toxic]

Simple test for a 750. Turn on the key and ground out the center of the neutral switch on the bottom right side of the crankcase. If you do and the switch comes on...Its the switch. If not more than likely the bulb or a connection somewhere.

Dang, thanks man now I know why my neutral light doesn't work.  Next time I have the pipes off I will change it out. I can't see it being done with the pipes on.

[Bill 350F]

I'm having a similar problem with a '72 CB350F. The bulb works. When I removed the sensor it was pretty clean. I wiped off a little gunk, reinstalled and still nothing. Attach the volt meter to the wire and ground, bike is in neutral, ignition switch on, no juice. How is this bulb powered? I've been looking at this wiring diagram and it connects to an emergency switch. Huh? Where's that?
(I've been looking at the schematic on the Old Man Honda page for the 350F, sorry it won't let me post a link)

[Bill 350F]

I'm going to have another go at it today. Any ideas?

[Oddjob]

I'm having a similar problem with a '72 CB350F. The bulb works. When I removed the sensor it was pretty clean. I wiped off a little gunk, reinstalled and still nothing. Attach the volt meter to the wire and ground, bike is in neutral, ignition switch on, no juice. How is this bulb powered? I've been looking at this wiring diagram and it connects to an emergency switch. Huh? Where's that?
(I've been looking at the schematic on the Old Man Honda page for the 350F, sorry it won't let me post a link)

Bulb isn't powered from the emergency switch, that's the on/off switch on the R/H handlebar switch, the red looking thing on the top, the diagram isn't clear but the neutral light is powered from the black wire, on Hondas of this time period black was the common power source, so the bulb is powered off a switchable 12v source, it won't light until the bulb is earthed, that's what the neutral light switch does. Remove the wire from the neutral light switch and hold it against the engine, the bulb should light, if it doesn't then the bulb has either blown, it has no power or there is a break in the green/red wire somewhere in the loom.

[Bill 350F]

Thanks. I actually did figure it out. I unwrapped a good portion of the harness, inspected the wires and found nothing. I went back to the bulb and took apart the housing and sure enough the solder on the black wire had broken off but the wire was still inside so by appearances it looked good. fired up the soldering iron and fixed it.

I guess I still don't understand the difference between the front stop switch and the emergency switch. I thought maybe there was some switch that trips if the bike falls over or something. Anyways it works now thanks again!