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SOHC.co.uk Forums => CB750 => Topic started by: Seamus on August 02, 2009, 09:44:49 AM

Title: CB750 neutral light
Post by: Seamus on August 02, 2009, 09:44:49 AM
Hello All,

My neutral light is playing up on the K1. It used to work prior to the rebuild, but now stays on. I have tried disconnecting at the switch to see if it is a short and it goes out. Occasionally it will now extinguish in 3rd gear. I guess the switch will have to come out, and hope that I don't have to drain the oil for this. Anyone know if they can be cleaned or is it time to replace it?

I was hoping it would just settle down and work and to be honest was more interested in getting everything alse tuned etc.
As I have not posted and pictures of the beast, I have attached one here.

http://i140.photobucket.com/albums/r31/Gearbox_photos/IMG_2056a.jpg[/img]](http://i140.photobucket.com/albums/r31/Gearbox_photos/IMG_2056a.jpg) (http://[img width=600 height=450)

Cheers

Seamus
Title: Re: CB750 neutral light
Post by: Spitfire on August 02, 2009, 09:50:55 AM
Hi Seamus, now that is a nice looking bike you have there, as to your neutral switch are you sure that the switch itself is located correctly ? On mine there is a definate right side up for the clip that holds the switch in place, though for about 20 odd years it was a chafed cable that made it stay on. When I was playing with mine I did not lose any oil removing it, check that it is working off the bike before you splash any cash.

Cheers

Den
Title: Re: CB750 neutral light
Post by: Seamus on August 02, 2009, 12:49:04 PM
Thanks Den. I fitted the switch when the engine was on the bench

See picture

http://i140.photobucket.com/albums/r31/Gearbox_photos/bottomcase.jpg[/img]](http://i140.photobucket.com/albums/r31/Gearbox_photos/bottomcase.jpg) (http://[img width=600 height=450)

So I am pretty sure that it is correctly fitted. I will pull it out and test on the bench. I just did'nt want to drain it down as I have just got it onto the road.

Cheers

Seamus
Title: Re: CB750 neutral light
Post by: steff750 on August 02, 2009, 09:24:18 PM
hi try tightening the 10 mm nut the holds the switch too the engine case it might have worked loose ,( if its the same problem i had ) and you shouldn't lose any oil if you have to remove the switch, it works off the gear selector drum its well up from the sump ,i think the switch has to earth to work the neutral light so it could still be  bad wiring
Title: Re: CB750 neutral light
Post by: Seamus on August 02, 2009, 11:31:37 PM
Hi Steff

I think I torqued the bolt as per manual at rebuild. It has not worked at all, unfortunately, but it is still worth a go in case I missed it. Thanks for the suggestion. If thid faile, I'll pull it out and bench test
Regards
Seamus
Title: Re: CB750 neutral light
Post by: Bryanj on August 03, 2009, 11:41:10 AM
You can take them apart and clean them but it only works 50% of the time, Dave Silver did have stock but they aint cheap 35752-300-020
Title: Re: CB750 neutral light
Post by: Seamus on August 03, 2009, 12:16:59 PM
Thanks Bryan. Worth a shot at cleaning again. I thought that I did clean it, but it worked when dirty ??? I did'nt have it apart though

Cheers

Seamus
Title: Re: CB750 neutral light
Post by: Yoshi823 on November 19, 2009, 10:10:42 PM
As there is +12v on the side of the neutral switch light,it is indeed the switch in the bottom of the crankcase that supplies the earth connection that lights the green light.
I would check the wiring from the loom to the crankcase switch.It sounds like an intermittant short somewhere.
Title: Re: CB750 neutral light
Post by: Seamus on November 19, 2009, 10:47:02 PM
Hi all
Fixed the problem. A bit of searching suggested that the replacement O ring is fatter than the original. I removed the switch and changed back to the original (luckily, I still had it). Refitted the switch and all worked.

That was a surprise  ;)

Cheers

Seamus
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