K1 Speedo drive.

[Mark]

Hi.
Another conundrum.
I don’t seem to have drive between the speedo cable and the drive mechanism.
The bevel gears on the rotating part seem in fine condition and turn ok when gently pushed with a small screwdriver.
The fixed gears attached to the wheel also look fine.
Spinning the cable in the speedo head by hand causes the needle to move suggesting the speedo itself works.
Fixing the cable to the drive and manually turning the gears does not make the cable inner turn.
I have to assume the problem lies in the connection from the cable to speedo drive.
The cable is old but the inner itself looks square enough at the point it enters to drive.
Can I safely disassemble the speedo drive rotating gear (46 03 17) - not the one fixed to the wheel - from the side cap (43 09 50) so I can have a look?
Any ideas of what may be the issue here gratefully received.

ps. I have raised clip ones and will need some slightly longer clock cables, ideally with a 20 degree kink at the top to clear the back of the headlamp. Any ideas where I might ask?

Cheers,
Mark.

[Ming]

If you rotate the drive gear in the 'snail' you should be able to see the cable driver rotating. Or, with it all assembled and the front end raised, rotating the wheel should give an observable rotation of the cable. Make sure the drive dogs are meshed with the gear.

[Mark]

I can’t see any movement at the cable end of the worm drive despite the worm drive gear itself turning ok.
Attaching the cable and turning the front wheel doesn’t turn the cable.
Re ensuring that the two sets of gears are meshing, I can’t see a way that they wouldn’t be as there’s only one way to assemble them, ie, the worm gear assembly drops over the gear attached to the hub and is fixed in position with the wheel spindle so assuming the gears are ok and were designed correctly in the first place they must be meshing - mustn’t they?
Anyway, as the worm drive doesn’t appear to be transferring movement to the cable end of the assembly even when detached from the hub drive gear I’m assuming the the problem lies with whatever lies between the worm gear and the point the cable attaches.
Can I safely disassemble the worm drive from it’s housing (there’s a 14mm nut there that suggests maybe I can) so I can have a look or am I looking for another worm drive assembly?
Or am I missing something obvious?

[Steve Brown]

Yes, it comes apart easily. Look out for the shim on the shaft. It is only one piece and it sounds to me that it's most likely worn. If you insert the cable inner in the speedo drive while it's all together and spin the wheel, you should not be able to stop the inner turning with your fingers. Once you strip and clean it you will probably see what's going on.

[Mark]

Thanks for the reply Steve.
Yesterday I checked another 350’s speedo drive so I now know I should easily see the cable end turning with the wheel.
This one doesn’t.
On inspection I can see why.
I can’t get the gear off the shaft (should I be able to?) but the gear itself is turning on the shaft, not turning the shaft, as if there should be a woodruff key or similar to lock it on the shaft but it isn’t there. Obviously if it isn’t turning the shaft, the shaft can’t turn the cable.
I can’t turn the shaft with pliers (carefully) either, suggesting the shaft is corroded in the body?
It looks as if I need another worm drive but I’d be interested if anyone can explain to me how this has come about - I’m now guessing the shaft rusted solid in the body during it’s 35 year sleep in a damp shed, causing whatever was locking the gear to the shaft to break when the front wheel finally turned again?
At the very least I’d like to know it isn’t something I’ve done on reassembly as if so I’m likely to do it again with the replacement.
Help!

[Steve Brown]

I can't say how they're attached, I've only ever washed them and refitted. Yes they should be fixed together though. I've no spares of these either-sorry.
Looking at another model yesterday I think I need to start making notes of the part numbers or codes on these drives. Sometime soon they will be getting hard to find and being able to identify any different ratios to suit different models will be useful.
At least you know what's wrong now and it won't be too difficult to get one. I hope!

[Mark]

Yes, I totally agree it would be good to know the code numbers/ratios etc for these drives.
As things are I’ll need to look for a drive for a 350 Morini but logically they must be the same on a lot of other Italian bikes of the period given that Veglia supplied most of the industry there at the time.

[3potjohn]

I have broken off from sitting in the sun on the hot side of the house and rolled about on the floor looking for an ID on my K1 speedo drive but perhaps due to having swigged some Korev lager I could not see one. My Coguaro however is 748200.

[Mark]

Andrew at Mdina had just one and it’s now fitted and running.
I was happy with £27.
The £19 postage was a bit of a surprise for something that would fit in a Swan Vesta box and weighs an ounce or two.
But not as big a surprise as the new post Brexit customs tax - 60% of the purchase and postage cost taking the total to about £73, more than three times the cost of the part.
I guess I’ll have to spend more time surfing ebay.it in future!

[hendre]

I know DHL charges an arm and a leg since Brexit to ship to the UK, maybe Poste Italiane does the same?

[Ming]

It's a lose / lose situation as far as I can see.