Author Topic: Speedo drive leak  (Read 746 times)

Offline Slippery Sam

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Speedo drive leak
« on: 24.01. 2017 12:31 »
A10, SA, STD gearbox.
Guys, I have an annoying leak from the speedo drive on my fresh build.
Is there anything I need to know or be aware of - things a novice would miss or not know?
Gearbox is a fresh reconditioned unit, fibre washers are new.
Do I have too much oil in there?
Is there a trick to tightening up the fittings?  I think to me it doesn't feel right when I've tried to nip it up a bit - hard to describe, sorry.  Am I missing a sequence or falling into a known common fault or something?
Worst thing is - the bike hasn't been off the bench yet - although I have run the motor and been generally finished a good few weeks - my registration still isn't sorted so not turned a wheel yet.
Any tips or things to check appreciated.
Raymond
BSA A10 Cafe Racer project
Scotland

Offline Topdad

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Re: Speedo drive leak
« Reply #1 on: 24.01. 2017 14:53 »
Raymond theres a  screw in the g/box outer cover which as a elongated end that stops speedo drive unit tight and should stop it turning when you tighten up the speedo cable .They wear and can still turn a new screw may fix it .If I remember the speedo unit is torpedo shaped to slide home and mesh with the drive from the layshaft ,I think it should have a rubber "o" seal which wears and allows leaks as well .
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Online Billybream

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Re: Speedo drive leak
« Reply #2 on: 24.01. 2017 14:58 »
Hi Raymond.
You will find chapter and verse on this subject.
I would check your oil level in the gearbox first, if ok you could fit an o ring in the end of the cable nut or try some silicon sealant.
Also it's best to secure cable into the gearbox before connecting into your speedo.
1960 Super Rocket, owned since 1966, back on the road 2012 after being laid up for 29yrs.

Offline Slippery Sam

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Re: Speedo drive leak
« Reply #3 on: 24.01. 2017 16:13 »
Thanks TD and Billy,
I think the best candidate so far is the locating screw.  The cable is new and the gearbox hasn't been in gear yet so it's a gravity thing.
From the feeling of the outer fixing nut - not really tightening as it needs to on the fibre washer - I suspect the bushing in that case might be getting pulled out (if not properly secured).  I just went over the parts diagram with a magifier and can see how it works now (always better when you know how it works!!!).  Think I'll give that a try - should actually have a new set of g/b outer case fixings so might well replace the offending item (if that's indeed the case).
Won't be tonight though - off on a welding course :-)  If the screw doesn't fix it I'll weld it in place (only kidding!).
Cheers Raymond
BSA A10 Cafe Racer project
Scotland

Offline Slippery Sam

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Re: Speedo drive leak
« Reply #4 on: 06.07. 2017 20:58 »
I've had a fiddle about with o rings, sealant and various methods.  Decided to take the whole drive bush out tonight - not an easy job and descended into strong arm tactics quite quickly.
The bush that came out was the brass type with no square seal (3396) and it was clearly a really tight fit in the gearbox.
Now that it's out I might have damaged the thread a little with my enthusiastic removal.  I could clean up the thread a bit and maybe treat myself to a new nut and fibre washer - but I might just replace it.
Is the later? Style bush with the square section seal on it interchangeable? Is the sealed type likely to keep the oil in any better?  The oil definitely wasn't coming from the inner bore (well pretty sure it wasn't) and the cable wasn't full of oil.
I'm keen to get it back together so itching to get a replacement ordered - just looking for a steer on whether to go plain brass or the one with a seal.
Cheers raymond
BSA A10 Cafe Racer project
Scotland

Offline duTch

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Re: Speedo drive leak
« Reply #5 on: 06.07. 2017 22:51 »

 Are they actually a square section 'O' ring, or round gone square from use? I went to buy a square section 'O' ring from the bearing/seal shop and the guy looked at me funny *eek*

 I thought they existed, and am still sure they do for some things
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Online Billybream

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Re: Speedo drive leak
« Reply #6 on: 07.07. 2017 04:31 »
You are not dreaming Dutch, square section O rings are called Quad rings or X rings, Nu-lip is another version.
They can achieve better sealing in both static and dynamic applications.
1960 Super Rocket, owned since 1966, back on the road 2012 after being laid up for 29yrs.

Offline duTch

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Re: Speedo drive leak
« Reply #7 on: 07.07. 2017 05:12 »

 Thanks B-B good information, I'll chase it up  *wink2*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline Slippery Sam

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Re: Speedo drive leak
« Reply #8 on: 07.07. 2017 07:58 »
Ironically, I'm asking if the bush with the square seal is interchangeable - I'd actually bought a couple of seals before I took the old bush out and found it was the plain brass bush.
I actually got the part reference off here.
It's a triumph part number as found on ebay.  57-0948
Not tried it yet - but looks like the correct part.

cheers Raymond.
BSA A10 Cafe Racer project
Scotland

Offline duTch

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Re: Speedo drive leak
« Reply #9 on: 07.07. 2017 08:35 »

 I can't give a full answer, but think I have two, and the brass one('modified') has a thread with a nut and the other (alloy/zinc-plated?) doesn't, this is the one in use.
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Online JulianS

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Re: Speedo drive leak
« Reply #10 on: 07.07. 2017 09:39 »
One of the most annoying leaks!

The early pattern brass with nut and fibre washer and later pattern zinc alloy 9with rubber ring) bushes do interchange. The new pattern repro for the zinc alloy version, is, I think now made from brass.

First photo the early brass, second the zinc alloy.

The leak is a common problem.

The first possible leak is between the bush and the outer gearbox cover. Cured either with new fibre seal under the external nut or by using the later bush. Oil runs down the outside of speedo cable and drips off.

The second possible leak is between the internal diameter of the bush and the speedo driven gear. This gets oil into the speedo cable and it drips out. The factory tried to deal with this by improving the fit of the bush/gear and then later added an O ring to the driven gear. See photo 3, O ring version at bottom.

The third leak is from the cable. usually seen where the alloy ferule joins the cable outer at gearbox end.  Some cables are better than others. those with a hex crimp ferule to cable seem to drip whereas those with a circular crimp usually hold the oil better. See photo 4 hex crimp at bottom. You can carefully seal betwen a hex crimp and cable outer using a bit of wiring heat shrink.

Offline duTch

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Re: Speedo drive leak
« Reply #11 on: 07.07. 2017 10:45 »

 
Quote
You can carefully seal betwen a hex crimp and cable outer using a bit of wiring heat shrink.
*between*

 I did that, but also think I have a combo of all (with 'O' rings), but don't have space on the Zn/Al sleeve for a lock nut  *scratches head*

 I guess they fixed the issue with the A65/50 series by running the Speedo drive from the rear wheel *bright idea*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline Slippery Sam

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Re: Speedo drive leak
« Reply #12 on: 07.07. 2017 13:52 »
I'm looking forward to giving this another go.  Bits and pieces ordered.
Raymond.
BSA A10 Cafe Racer project
Scotland