Author Topic: Speedo drive into gearbox  (Read 825 times)

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malzstx

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Speedo drive into gearbox
« on: 20 March, 2017, 18:36:48 »
The speedo drive cable of my Super Rocket screws into what appears to be a threaded nipple at the base of the gearbox and it looks like I have a slight oil leak from the nipple. My question is; is this nipple screwed into the front cover or is it part of the casting? the nipple has no flats to tighten it with a spanner, but is ROUND and won't move with a pair of water pump pliers. Thanks in anticipation....Malcolm.

JulianS

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Re: Speedo drive into gearbox
« Reply #1 on: 20 March, 2017, 19:08:25 »
The "nipple" will be either brass or zinc alloy it is called a bush. It is a tight fit in the case and is held in position by the screw indicated in the first photo.

If its brass there is probaly a nut and fibre washer on the threaded end to seal. If zinc alloy there will be an internal o ring.

Usually the leak is oil seeping between the bush and the speedo driven gear shaft - the bit into which the cable inner fits. It then drips out of the cable where the ferrule is crimped to the cable.

Second photo shows brass bush and third the zinc alloy version. The groove for o ring can be seen closed threaded end.

To remove bush first remove the retaining screw and use an old speedo cable screwed on to pull it out. A bit of heat may assist but usually its not too tight and will either pull out or tap off with a rubber mallet.

malzstx

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Re: Speedo drive into gearbox
« Reply #2 on: 20 March, 2017, 20:49:30 »
Thanks once again Julian.....clear as a bell! your knowledge has helped me on so many occasions. Is there anything you don't know about BSA's?........Massive thanks ....Malcolm.

JulianS

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Re: Speedo drive into gearbox
« Reply #3 on: 20 March, 2017, 22:05:26 »
Malcolm

Thank you.

I hope it helps.

If you need to take it out its best tackled after removing the outer cover from the gearbox, especially when putting the bush and driven gear back in.

If its just the oil leaking from the cable ferrule then that can be sorted by use of a bit of 10mm heat shrink cable sleeve. Disconnect the speedo cable from gearbox. Slide the sleeve nut back along the cable.Take about 30 mm of heat shrink and slide it on to the cable covering the join between cable and ferrule but the only bit of ferrule to cover is the crimped part. Shrink it tight over the join by your chosen heat source then carefully slide the nut back into position - its a bit tight and you need to be careful not to damage the sleeve but it can be done. I use a squirt of WD40 to help.

That should stop oil dripping from the cable.

RICHARD MILLS

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Re: Speedo drive into gearbox
« Reply #4 on: 21 March, 2017, 16:07:45 »
I had thought of using heat-shrink tubing as suggested on my B33, but decided not to do so in case the oil that was then retained in the cable got 'pumped' up to the speedo by the revolving action of the inner cable.
Replacement bushes are easy to find. Not so for the spindle, however I eventually managed to get a NOS one which took an 'O' ring; trouble was that it was in America!

JulianS

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Re: Speedo drive into gearbox
« Reply #5 on: 21 March, 2017, 18:15:29 »
The O ring on the driven gear does help but it is a bit flimsy.

I fitted one on my A10 but it did not entirely cure the leak hence the use of the heatshrink.

So far have not had oil in speedo head and, being aware that it is a possibility I remove the inner and check it occasionally.

New old stock O ring shaft and bush shown in my lower photo.

Looks like the factory tried to solve the leak by tightening tolerences
« Last Edit: 21 March, 2017, 19:05:27 by JulianS »

RICHARD MILLS

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Re: Speedo drive into gearbox
« Reply #6 on: 22 March, 2017, 09:38:46 »
I only fitted the 'O' ring spindle at the end of last year and have yet to see how it performs (it does seem to have let a little through during its over-winter lay-up).
Rather than keep checking the cable for oil, I plan on letting any that gets through just drip out!

JulianS

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Re: Speedo drive into gearbox
« Reply #7 on: 22 March, 2017, 10:23:50 »
I usually just check when changing engine oil and so far have had no noticable oil in the cable, just the normal lubricating grease.


malzstx

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Re: Speedo drive into gearbox
« Reply #8 on: 24 March, 2017, 18:06:50 »
Hi Julian.....job done as per your instructions. Filled gearbox and completely oiltight. I didn't have the correct seal so used two thin 'O' rings.....perfect. Thanks once again for your help. Malcolm.