750 ND horn button and handlebar switch

New relays installed and issue with lights now fixed. Opened up the old dodgy one but can't see anything wrong with it.
Been in touch with Rex mentioned above and he can supply all replacement Rita parts made from modern components, ideal for a spare and will probably fit one to the GTL.
 
On arriving home from my weekend away at the Laverda gathering in Austria I found my horns had died.
Whilst trying to find the issue, I came across this thread so I thought I'd add my two-peneth.
Testing the horns with a separate battery, one still worked whilst the other just sparked when I touched the tabs with the probes.
I suspected the earth from the lh handlebar switch (not shown on the wiring diagram) on delving deeper the black/white wire just ended in the sheathing 😮.
Adding a dedicated earth wire from the bike frame to the switch has brought the working horn back to life through the button.
So just waiting for replacement horns and an M3 ring connector so I can put everything back together.
I hate electrics 😆
 

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russo011 said:
On arriving home from my weekend away at the Laverda gathering in Austria I found my horns had died.
Whilst trying to find the issue, I came across this thread so I thought I'd add my two-peneth.
Testing the horns with a separate battery, one still worked whilst the other just sparked when I touched the tabs with the probes.
I suspected the earth from the lh handlebar switch (not shown on the wiring diagram) on delving deeper the black/white wire just ended in the sheathing 😮.
Adding a dedicated earth wire from the bike frame to the switch has brought the working horn back to life through the button.
So just waiting for replacement horns and an M3 ring connector so I can put everything back together.
I hate electrics 😆
Click to expand...
Good to read you got yourself sorted.
 
russo011 said:
Testing the horns with a separate battery, one still worked whilst the other just sparked when I touched the tabs with the probes.
😆
Click to expand...
I've found over the years that horns react well to percussive maintenance. Mine are still the OEM ones, still working well after fifty years.
Connect a power supply and then tap (clout) the horn with a rubber mallet, a couple of times. a small variation on the tuning screw, on the back, also helps.
This, like CPR, often restores function.
If that doesn't work, drill the rivets and remove the cover and clean and lubricate the innards. Gives you as chance to clean the alloy disc, too Re-assemble with button-head Allen screws with nuts and spring washers.

Horn Refurb 1.JPGHorn Refurb 2.JPGHorn Refurb 3.JPGHorn Refurb 4.JPGHorn Refurb 5.JPG
 
You've done very well to keep your original horns going Hamish,i'm on my second pair in 9 years and i still can't get them both to work together on the open road!
In the garage they work together but when needed in anger not a sound unless I disconnect 1 of them......so during the winter lay up i'm going to knuckle down and try and fix them once and for all.....i hope. 🤔
It could be an earth issue,could be a wiring issue (series or parallel) I just don't know......relays fitted.
 
Most motorcycle horns are pretty pathetic at the best of times even on the newer bikes. The voxbell being no exception.
When the originals on my bike gave up the ghost I replaced with new voxbells which ended in tears, tried every thing and I could not get either pair to work.
In the end I pinched a pair of yamaha horns from a 650 turbo project I had, gutted one pair of voxbells etc.....
Now have a pair layam poxbells fitted that still work after many years of rain and shine.
From the outside they look like a pair of voxbells.;)
 
Schurminater said:
You've done very well to keep your original horns going Hamish,i'm on my second pair in 9 years and i still can't get them both to work together on the open road!
In the garage they work together but when needed in anger not a sound unless I disconnect 1 of them......so during the winter lay up i'm going to knuckle down and try and fix them once and for all.....i hope. 🤔
It could be an earth issue,could be a wiring issue (series or parallel) I just don't know......relays fitted.
Click to expand...

Sounds like a typical case of excessive voltage drop to me. Try thicker cables from battery to horn (via the relay), and thicker earth cable. Horns draw a fair bit of current and the original wire sizes are pretty marginal. They're the most current-hungry device on the bike after the starter motor. It works with one horn because that only draws half the current, so voltage drop in the wiring system will be less.

Check that it'll fix the problem by connecting decent jumper cables directly between the battery and horn before you delve into modifying the bike's wiring system. If it doesn't, then the problem could be within the horns themselves, or a battery that isn't up to par.
 
Many thanks for the advice I will certainly look into that,I am using the original or as near as loom wiring for the horn circuit.
When you say a thicker cable from the battery to horn (via relay) should I have run a new direct feed wire 12V from the battery to the relay? ignoring the original horn feed?
 
Schurminater said:
Many thanks for the advice I will certainly look into that,I am using the original or as near as loom wiring for the horn circuit.
When you say a thicker cable from the battery to horn (via relay) should I have run a new direct feed wire 12V from the battery to the relay? ignoring the original horn feed?
Click to expand...
Is the relay a high enough rating, for the current requirement of the horns?
 
The Sock said:
I've found over the years that horns react well to percussive maintenance. Mine are still the OEM ones, still working well after fifty years.
Connect a power supply and then tap (clout) the horn with a rubber mallet, a couple of times. a small variation on the tuning screw, on the back, also helps.
This, like CPR, often restores function.
If that doesn't work, drill the rivets and remove the cover and clean and lubricate the innards. Gives you as chance to clean the alloy disc, too Re-assemble with button-head Allen screws with nuts and spring washers.

View attachment 107560View attachment 107561View attachment 107562View attachment 107563View attachment 107564
Click to expand...
Best horn maintenance is to actually use them now and again... when out in the open and nobody can be offended, hold the button for 5-10 seconds, repeat a couple of times. The magnets operate at a pretty high frquency, any crud or rust will be simply hammered/shaken away.

Although adequate when new, the stock loom cables can deteriorate to the point where internal resistance rises to the extent that the horns are supplied with 8-9V at best, a sickly croak is all that can be expected. The old cables are still ample for powering a relay and a new, substantial supply to and from the relay to the horns restores the noises.

piet
 
When you go into an automotive parts shop to buy a relay, the usual default is little black plastic thing rated at 12V 30A which would be perfectly OK. The horns are not going to pull that much current.

I don't remember whether I've ever measured the current drawn by a Voxbell horn, but I'd expect it to be around 5A per horn, so if you work on a max of 10A for the two, you should be in the ballpark for wire size.

The normal wire choice for 10A would be 2.5 mm². That's substantially thicker than the original Laverda horn wire, which looks like about 1.0 - 1.5 mm². I guess the the factory designers figured the horn is only energised for about 1 second on the occasions that you press the button, so the cable won't overheat in that brief time. Maybe they figured the voltage drop would be acceptable in a new system with clean connectors, no frayed wires and horns in good condition.

I just noticed that Piet posted while I was typing and he said pretty much the same thing about the original wire size.

The power wire for the horn doesn't necessarily need to go all the way back to the battery. It can be taken from the fused side of the fuse box so long as the cable from the battery to the fuse box is a decent heavy one. If your fuse supply wires are less than 2.5 mm² (I rewired my bike many years ago and don't recall the original size), then you're better off taking the horn feed direct from the battery, or from the battery side of the starter relay. Of those two options, I'd go for the starter relay just to avoid a nest of wires around the positive battery terminal.

If you connect to the battery or starter relay, I'd also recommend fitting an in-line fuse as well, as close to the source as practical. Some relays come with a built-in fuse that would be a simple and neat solution.

Enjoy your wiring ... ;)
Cam
 
russo011 said:
On arriving home from my weekend away at the Laverda gathering in Austria I found my horns had died.
Whilst trying to find the issue, I came across this thread so I thought I'd add my two-peneth.
Testing the horns with a separate battery, one still worked whilst the other just sparked when I touched the tabs with the probes.
I suspected the earth from the lh handlebar switch (not shown on the wiring diagram) on delving deeper the black/white wire just ended in the sheathing 😮.
Adding a dedicated earth wire from the bike frame to the switch has brought the working horn back to life through the button.
So just waiting for replacement horns and an M3 ring connector so I can put everything back together.
I hate electrics 😆
Click to expand...
I would advise fitting a separate relay for the horns and using new wires. I have one with a built-in fuse. The horns draw a lot of current, which can fry your switch or connectors. My horns received 6 Volts at the terminal. Nary a squawk. Lots of fried insulation inside the headlight.

IMG_5227.jpeg
 
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