advice on best way to cure these leaks

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Dec 5, 2007
Hi, I am going to make a concerted effort this winter to to resolve three annoying oil leaks. The first two are from the kickstart shaft and gear lever on the outer gearbox cover ( pre mk3) I have checked out the history of this topic on the forum but are unsure of the best way forward. Lip seals are recommended by some owners for the kickstart shaft leak.Does this involve engineering work - if so could some one tell what needs to be done and where is the best place to get the seal (uk) Other owners recommend the use of an X ring - where can these be purchased. What about the gear lever shaft - is this a case of using a lip seal and could anyone supply me with a code no. for it . If I was to go this route what engineering work needs to be done and where do I get the seal from. Alternatively is there an X ring available for this.. Finally I have a leak at the top of my rev counter drive I understand that this too can be rectified with a little engineering work and a different seal could anyone please supply details. I have contacted RGM about getting this work done but they are snowed under with work and it could take a (very) long time. Thanks in anticipation.
Hi there, I have solved the kick start shaft leak with the simplest way by changing the previous rubbish o ring with a quad ring (and as you are british, you can order it through norvil, I do not have the reference right now under hand), another way could be to fit a breather (as per late gearbox shell ) on the top of the gearbox shell nearby the clutch cable hole, if you don't have any , that could be the reason of your leaks , mainly through the gear shaft which is obviously above the oil level (and the kick start shaft isn't ), hope my english is good enough for a frog;; Pierre
Yes the quad ring is available from Norvil, (part 069595) the alternative is to have the cover machined to take the 850 Mk3 kickstart seal (066145). I know that RGM also offer a gear lever shaft seal but I'm not sure which seal is used for this, and I expect Norvil would also be able to offer this conversion including any machining work.

The rev counter drive is easily modified by fitting a lip seal, a Honda seal is commonly used I think, but any correct size seal should should do, I modified my own drive using an unidentified 14x7x4mm lip seal that just happened to be laying about amongst my stock of spares.

However, I think I would speak to Mick Hemmings first, as he will probably be able to offer the same things, and (Mick & Angela) Hemmings can be a little more 'customer friendly' and likely to deal with you on a more personal level than Norvil possibly will, Mick of course is a true Norton expert, but I wouldn't want to put you off dealing with Norvil as Mick could also be very busy?

Mick Hemmings Motorcycles:

If the bushes in the outer cover are reasonably OK then a conventional lip seal is quite adequate for these applications.

There is a small amount of machining work but any local engineering firm could do this, it doesn't have to be a specialist if you supply the seals and tell them what you want.

Although the earlier covers don't have the raised boss that the Mk111 has, this is not a problem and the mod is almost invisible once the levers are fitted.

The tacho housing can be turned out on a modelmakers lathe if you know someone with one. The seals will be about 50p from a bearing supplier. I have 16x7x7 in mine simply because this was the size that someone who'd done it before gave me the first time. The seal is not a permanent cure as it will harden over time. I find they need changing every 15 years or so :D
79x100 said:
The tacho housing can be turned out on a modelmakers lathe if you know someone with one.

Some may throw their hands up in horror at this, -but I used an electric hand drill and 14mm drill bit, and then stuck the seal in with stud-n-bearing fit!

I did actually try to lever the seal out some years afterwards (for no good reason), but it didn't want to budge, so I left it alone.
I also have a std lip seal behind the bush which is a 1" x 1-1/4" x 1/8". That needs no machining but does need to be glued in place. Silicone does not work for me, eventually oil gets by the OD so I now use cyano' to retain and seal. The Norvil X ring is probably an improvement over the 'O' ring. For the gearchange, as long as the bush is good leaks from here are rare. I have a breather on the inner cover though.
On the tach drive some PO had modified for a 14,5 dia seal from ATE so it looks like they'd used a brake part and I could not find this size anywhere when it finally failed this year. Had to use the Norvil 14,0 item, now held in the oversize bore with cyano' again. Just make sure that the shaft gets greased above the seal as with no leakage they can seize.
I tried the tach drive oil seal conversion on my 750 but it didn't work. It leaked so bad I took it off and put the o-ring one back on :?

The seal did feel a little too loose in the bore. Maybe it needs to be fixed in place with loctite or crazy glue? (now there's something I wouldn't have thought of by myself!)


Did you install the seal with the lip towards the engine?

advice on best way to cure these leaks
Ron L said:

Did you install the seal with the lip towards the engine?

Yes, but my tach drive and housing don't look like the ones in your illustration. The drive shaft does not have that o-ring groove half way up, and the housing does not have the conical-shaped inner bore. Also, the seal supplied with mine was a Honda part.

At some point Norton changed the tach drive, adding that second o-ring in an attempt to stop the leak. Did the shaft diameter change also? The Honda seal did not seem to be a very snug fit on either the drive shaft or in the housing.

BTW I did replace the drive gear with an NOS part as there was noticeable wear on the shaft where the o-ring fit. That had no effect on the leakage however.

Since the body is aluminum and the drive gear steel, if the drive gear was worn, the aluminum body must have been worse!
Ron L said:
Since the body is aluminum and the drive gear steel, if the drive gear was worn, the aluminum body must have been worse!

D'oh! That never even occurred to me! I'll have to take a look at it. Might be hard to find a replacement though, with Andover only making the newer-style parts. (Not sure about compatibility.. :? )

Even the new bodies can have very rough and poorly tolleranced bores, so if you can check them out before you buy. I've always thought this was the major cause of tacho drive leaks. The last new drive body I fitted was 12 years ago. I bronze bushed it to the correct finish and fit, added the usual lip seal and its never leaked a drop.

I'll probably leak now.

dealing with oil leaks - definitively

I have a 2007 Harley - no leaks.
A 2001 BMW - no leaks.
Previous non-Brit bikes: Hondas, etc. - no leaks.

Current bike; 75 Commando - leaks prodigously.
Prev Triumphs and Nortons I owned - ditto.

Moral of the story - if you want a bike that doesn't leak oil, buy a Honda. Guaranteed solution. But if you own a Brit bike and actually ride it, say 4,000 miles a year, as I do - it will leak oil. Period.
You can chase solutions till you drive yourself crazy - or just ride, enjoy, and keep topping off the oil and be careful whose driveway you leak on.
The bronze bush sounds like an excellent idea! It's too bad Norton didn't think of that rather than adding another o-ring!
Re: dealing with oil leaks - definitively

pkeithkelly said:
But if you own a Brit bike and actually ride it, say 4,000 miles a year, as I do - it will leak oil. Period.

They should "sweat" a bit, that's what gives the characteristic smell in the garage but they shouldn't "leak"

The oil seal mods being talked about here simply bring the gearbox up to Mk111 spec and cure the tacho problem which can be a messy one but really doesn't have to be.

I recall a reader's report in, I think, "Bike Magazine" back in the '70s. A young chap bought a brand new Triumph which lost oil and when he took it back to the dealer and told them he had an oil leak, the old mechanic scratched his head and said "That's not leaking son, that's pissing out !" :)
Well I've spent a few years trying to make my Commando leakfree and it's now dry as the proverbial bone. OK, it took a belt drive to complete the challenge but with a non return breather and other minor mods any engine fasteners that aren't stainless now go rusty . It sees 3000-3500 miles a year, lots at 75-80 + so it does a bit of work. It is possible to stem a 'total loss' Norton. Might be harder on Triumphs though and I had a couple of those a long time back.......
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