Author Topic: Final Drive Seal  (Read 355 times)

Offline AndyD

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Final Drive Seal
« on: July 07, 2024, 11:16:58 AM »
Hi,
Trying to get the CJ250t ready and on the road but another snag now with an oil leak.
Thought originally it was the gearchange lever seal - replaced this but leak returned straight away.
Running with engine side exposed shows the leak is from the final drive seal.
I think I know the answer but just wondered (hoped) if there is any way to replace this without splitting the crankcases etc.
From the parts drawings the seal appears to have a locating nipple but can't recall if it also has any lip set into the cases.
Advice very welcome
Cheers,
Andy

Offline Laverda Dave

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Re: Final Drive Seal
« Reply #1 on: July 07, 2024, 12:20:14 PM »
I feel your pain Andy, same happened to me on the original build of the CB250RSA, the lip seal tore around the shaft and caused the leak.
I read up about pulling the old seal out using wood screws drilled into the seal itself and cutting the nib off the new seal but in the end I thought I'd rather do the job properly rather than risk another potentially catastrophic seal failure. I had to separate the cases but it wasn't too bad as the head and barrel etc could remain in situ. It took me an afternoon in the end (excluding getting the engine out and back in again).
1976 Honda 400/4
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1978 Honda CB400/4 'Rat' bike
1982 Laverda 120 Jota
2020 Royal Enfield Interceptor 650

Offline AndyD

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Re: Final Drive Seal
« Reply #2 on: July 07, 2024, 02:06:39 PM »
Thanks Dave,
Guess I'm pretty well resigned to having to strip her down again although I may put it off a while to rebuild some enthusiasm.
Was hoping to finally get some riding in this last few weeks and even bought a new helmet and gloves thinking the 250 would be ideal for start - best laid plans and all that!

Like you I'd seen a few stories of replaced seals without dismantling but doesn't really sound right somehow and always best to do it right.

I can't recall if it's possible to split the cases without stripping the top end at least saving a few gaskets and jobs! Will have to have a look at that and see what makes sense.

In the meantime must get busy with clearing some space in the garage and sheds - too many bikes / projects / spares and waning enthusiasm so think it's really about time for decisions on what to keep and what to get rid of.

Cheers,
Andy

Offline Bryanj

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Re: Final Drive Seal
« Reply #3 on: July 07, 2024, 02:29:59 PM »
You can split bottom case off and leave everything top end intact

Offline AndyD

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Re: Final Drive Seal
« Reply #4 on: July 07, 2024, 02:56:55 PM »
Many thanks Bryan,
That should save a lot of grief (and cost) hopefully.
Just have to summon up the enthusiasm to drop the engine out and get on with it.

Cheers,
Andy

Offline Laverda Dave

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Re: Final Drive Seal
« Reply #5 on: July 07, 2024, 10:34:03 PM »
If you need a hand Andy let me know, happy to provide some lifting power to get the engine out (and back in).👍
1976 Honda 400/4
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1978 Honda CB400/4 'Rat' bike
1982 Laverda 120 Jota
2020 Royal Enfield Interceptor 650

Offline AndyD

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Re: Final Drive Seal
« Reply #6 on: July 08, 2024, 05:29:12 PM »
Thanks Dave,
I may well take you up on the offer if that's OK - always fiddly getting the lump in and out without damaging all the shiny stuff!
I'll get the bits needed and try and formulate some kind of plan.

Cheers,
Andy

Offline Laverda Dave

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Re: Final Drive Seal
« Reply #7 on: July 08, 2024, 10:03:52 PM »
No problem Andy, I'll be glad to help and with both of us on it we can hopefully get it out and back in within a day. A lot of effort to undo a few bolts to replace a seal worth £10 but worth doing properly just for piece of mind👍
1976 Honda 400/4
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1978 Honda CB400/4 'Rat' bike
1982 Laverda 120 Jota
2020 Royal Enfield Interceptor 650

Offline AndyD

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Re: Final Drive Seal
« Reply #8 on: July 09, 2024, 12:33:53 PM »
Thanks Dave,
I'm just thinking if I'll need to order any other bits beyond the oil seal for this.

If only going in from the underside (i.e top end untouched) I'm hoping the other oil seals etc. affected when splitting the crankcases can just be retained.
I'll have a study of the parts drawings and photos to see what could be affected.

Cheers,
Andy

Offline Laverda Dave

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Re: Final Drive Seal
« Reply #9 on: July 09, 2024, 01:51:16 PM »
Hi Andy.

You'll likey need some Hondabond to rejoin the cases and some cellulose to clean the old hondabond off. Trouble is Hondabond goes off in the tube once opened, the tube I bought a couple of years ago was rock solid when it came to refitting my 400 cases, luckily I was able to to cut the tube open and rescue some from deep within the tube using a thin brush.  You may need new gaskets for the side casings but if the bike hasn't been run they should be OK.
1976 Honda 400/4
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1978 Honda CB400/4 'Rat' bike
1982 Laverda 120 Jota
2020 Royal Enfield Interceptor 650

Offline Bryanj

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Re: Final Drive Seal
« Reply #10 on: July 09, 2024, 03:14:55 PM »
The other seals can be replaced easily later if necessary, maybe a clutch cover gasket if it rips, i usualy like to fit new but as its nearly that you may well get away with it

Offline McCabe-Thiele (Ted)

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Re: Final Drive Seal
« Reply #11 on: July 09, 2024, 05:24:32 PM »
Not sure if its the original seal that has just started leaking or if its after a rebuild.
My only experience  based on oil leaks from ADO15 Mini drive shaft output seals that started to leak is there is often a cause for seal failure. On the MIni it was due to wear in the differential that caused the seals to fail due to excess movement on the output shaft bearings.

If its just old age or damage when fitting a replacement should work - just make sure its not caused by excessive demands due to excessive shaft movement or corrosion on the shaft externals. Sorry if i'm stating the obvious.

Honda CB500 K1 (new pit dug out ready)
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html
This is a neat 500 restoration in the USA.
http://forums.sohc4.net/index.php/topic,151576.msg1731556.html#msg1731556

 

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