Narrowcase sprocket bearing

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ranton_rambler
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Narrowcase sprocket bearing

Postby ranton_rambler » Sun Mar 04, 2018 8:51 am

I'm about ready to fit the new bearings to my cases now (175TS). The new output bearing that sits behind the sprocket is a sealed type, where the original was not. I've heard that the little oil drain passage should be closed off when using a sealed bearing. Any thoughts on whether this is true, and what should be used to close it off? I was thinking some Chemical Metal or similar.

Ian

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Bevel bob
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Re: Narrowcase sprocket bearing

Postby Bevel bob » Sun Mar 04, 2018 7:27 pm

There should be a pen steel washer in there ,I left mine out when i fitted a sealed bearing, but then wished I had not as it has leaked ever since.

ranton_rambler
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Re: Narrowcase sprocket bearing

Postby ranton_rambler » Sun Mar 04, 2018 8:18 pm

I've been advised to leave the washer out, but block up the little oil return passage.

Bevel bob
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Re: Narrowcase sprocket bearing

Postby Bevel bob » Sun Mar 04, 2018 10:07 pm

If its not broke!, You think its a drain, I think its a supply. Perhaps to lube the drive chain?.

Samurai
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Re: Narrowcase sprocket bearing

Postby Samurai » Mon Mar 05, 2018 6:53 pm

I too was advised by Nigel Lacey to leave the washer out but to seal the hole, which I have done with a high temperature silicon jointing compound. I have only just managed to get the bike started reliably this weekend, but have not yet noticed any leaks from that area - a few small weeps elsewhere though!

Nigel also mentioned that leaving the washer out would have the minor additional benefit of allowing the bearing and thus the drive sprocket/chain to move away from the edge of the chain 'tunnel slightly', as this often gets chewed up with a poorly aligned or slack chain. He's been doing this on his race bikes for years and never had an issue, so if it's good enough for him, then who am I to argue?

Bevel bob
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Re: Narrowcase sprocket bearing

Postby Bevel bob » Mon Mar 05, 2018 7:23 pm

Race bikes do not need a chain oiler. Looking at it I can't see its anything other than a supply to the chain with the pen washer restricting the flow to a minimum. The majority of these bikes were intended to go to the States where bike maintenance was often minimal and the result of a broken chain was often severe damage to the clutch mechanism. Classic use means chains are maintained more often than not so the feature is perhaps an annoyance now that most bikes are just polished and posed.Taglioni was no fool. Mine will go back in if I get the chance.

LaceyDucati
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Re: Narrowcase sprocket bearing

Postby LaceyDucati » Mon Mar 12, 2018 8:26 pm

Bob
An oil leak from the drive sprocket will lube the chain, but probably the tyre and your drive too. Chain oilers are usually smaller from what I've seen.

The sprockets have a left hand scroll that will try and push any oil back into the cases. The thin washer behind the bearing will centrifuge the oil into the space behind the bearing, which will then drain from this space back to the sump via the slot under the bearing. All these directions of movement of oil would indicate oil movement is in the opposite direction of chain oiling. However as a sealing method in theory it should and does sometimes work, but under race conditions it mostly doesn't.

Regarding Taglioni being no fool, then maybe that's why he dropped the scroll and drain on the Widecases. I expect the thin washer was retained with respect to sprocket positioning. The later Spanish models lost this washer and went for a sealed bearing retained with a circlip.

My recommendation is to use a 2RS (contact seals) bearing retaining both seals and with the slot sealed. I personally leave out the washer as well, as I think it gives an extra slip (and leak) face and places modern HD chains too close to the selector box inner cover. I've been doing this for nearly 30 years now and it works for me.

Best Wishes Nigel

ranton_rambler
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Re: Narrowcase sprocket bearing

Postby ranton_rambler » Sun Mar 18, 2018 10:40 am

I've now sealed up the little oilway with some high-temperature epoxy. Hope it will be OK...........


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