Topic: CB750 Horn Rebuild?

[edwardmorris]

Search came up with just one post that went nowhere, so here it is, quite possibly a dumb question.

In the interest of preserving as much of the original bike that is still functional, is it worth rebuilding the horn and more importantly, can it be done? It looks like a pretty sturdy assembly, but then again, so were the gauges. Mine looks like it has collected a lot of dirt and debris along with severe pitting on the chrome dome. Has anyone done this around here?

[skidooextreme]

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[ekpent]

If it does not work or is rusted up really badly on a later model machine I would probably just source another off of E-bay or here. If it was an original Sandcast or unmolested K0 than worth investing time and money. There is a way to adjust them if the sound is way off.

[edwardmorris]

It works and sounds right, but the chrome cover looks awful with all the rust. I'm gonna clean it up and see if it looks any better. NOS one's aren't cheap, and I'd rather keep as much of the original stuff intact. If I could get the chrome dome, then I can see how bad is it inside.

[bjbuchanan]

I would suggest that you post a wanted ad because plenty of us have stashes of parts. None of us are usually particularly attached to a "good" horn

Unless you live in china that chrome is gonna cost too much IMO

[AJK]

My horn died and was sounding like a dying duck. So i decided to pull it apart, clean it up, reassemble and give it a coat of black. Now it works great. The 103db's are really coming through.

Basically they are a 103dB unit, 12V @ 3Amps. In case your wondering, the following pictures show what you can expect on the inside.

Picture #3 - Shows the internal solenoid mechanism. There are a pair of contacts in there. They were cruddy. I cleaned them up with wet'n'dry and cleaned them with some WD40, then dried them up.

Picture #4 - Shows the outside of the actual horn plate. This plate is metal and is the actual sound maker that vibrates.

Picture #5 - Shows the inside of the horn plate. This side fits into the solenoid mechanism shown in picture #3.

Picture #6 & #7 - A quick preparation of wet'n'dry on the metal mount and then wax and grease remover on the whole lot that will be painted.

Picture #8 - Is picture #6 is literally one minute later with 1 coat of white knight epoxy enamel. I love this stuff.

These are quite recoverable, so give it a go. Treat the round gaskets with care and you'll be good to go. Hope this helps.

cheers
Alex

[ekpent]

Nice post AJK-- That's some good info well documented. Never took a peek inside one yet.

[AJK]

Thanks ekpent,

It was pretty much dead & an obvious thought was to trash it. I was tempted to get an aftermarket generic motorcycle horn ebay (for ~$15 or so), and mount it under the seat somewhere out of sight, but at the same time keeping the original for looks. Then i thought that there shouldn't be much in the original horn, may as well try and salvage it if possible. Not knowing what to expect, its turns out that they are a very well constructed unit & well worth saving. Definitely shouldn't be thrown out. The bonus is that you don't have to detract for the original look of the bike using the original horn once you service it. I.e. Not needing to go aftermarket.

The main problem was the contacts & I think this is really what causes problems in the first place as there really isn't much in them.

I might end up using a relay to drive it in the future to be gentle on the switch, but for now at least it works and might even save me one day.