Honda-SOHC

Good Day All -

I'm hoping one of you can help diagnose the cause of what I believe to be a clutch or transmission whine emanating from my newly rebuilt CB400F. It can be heard only when power is being transmitted to the rear wheel - i.e., there is no noise in neutral, or in gear with the clutch disengaged but if I place the front wheel against a wall and feed in the clutch a little, the whine becomes apparent. When getting underway and accelerating, it is quite pronounced but at steady roadspeed, it reduces somewhat. On trailing throttle, I can't hear it at all. Clutch operation is smooth, with no dragging or slipping, she snicks up and down through the gears nicely and neutral is easy to find.  Search results from the two forums suggest it may be normal or it may indicate imminent catastrophic failure! Hopefully the video will help narrow it down.

https://youtu.be/2tdTc9uSn_U

Full disclosure, here: after reassembling the clutch, there was a part left over I wasn't too worried at the time, as I couldn't see anything resembling it in the parts manual exploded view and it wouldn't have been the first time a part from the CB450S my step-son was rebuilding in the same shed found its way into the my 400F's parts bins. I'm thinking now it might be relevant. Can anyone identify the part?

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Hopefully, the noise is coming from the clutch, as otherwise I'm afraid I'll have to split the cases again and I really don't know what I'd be looking for as all the bearings were replaced during the rebuild!

Thanks and Regards,
Brian

Hi Everyone -

Man! Sometimes I don't know how I make it through the day...

I took this engine apart a little over a year ago. Now it's back together and has actually run for a few seconds - sans pipes -  to check that the new wiring harness and elecktrickery pieces were connected correctly. I was about to fit the header with new exhaust gaskets when it struck me that I don't specifically remember taking the old ones out during disassembly. I might have done so, but it was 14 months ago and my memory isn't what it used to be 

If anyone has a bare 400F head in the shed, would you mind having a look and comparing it to mine? I don't want to possibly damage any sealing surfaces by trying to gouge out a gasket that might not be there!

Thanks and Regards,
Brian

Good afternoon, everyone -

I'm in the process of rebuilding a '75 CB400F and have reached the point of installing a new wiring harness sourced from David Silver Spares' U.S. outlet. I obtained new right and left handlebar switches from 4into1.com and everything seemed to snap together just fine with only a couple of things making me scratch my head. I should mention here that electrical is not my strong suit 

There are three unused bullet connectors in the bundle which resides aft of the steering stem under the tank. The light blue/white and orange/white wires I believe should be connected to the front directional indicators when I install them but the remaining blue/brown is a puzzle. The wiring diagram I have seems to show a blue/brown running in one direction to the tail-light fuse and in the other to a black multiple connector and thence to the horn? Do I connect the horn to this wire?

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One more quick question while I have your attention 

The wiring diagram shows a red/green wire from the clutch switch. The replica LH handlebar switch I got from '4into1' does not have a clutch switch - I assume ( ) that I can simply jump the red/green from the harness in the headlight to any of the many available green wires also in the headlight shell to make it work?

Thanks for your help,
Brian