Clutch slave O-ring questions again!

1200ts

1200ts

Hero member
Location
USA - Riverside CA
I was hoping my last post would clear up the confusion but it has only made it worse. The question was about the size of the clutch slave O-ring. After my last post and searching through old posts about this topic, I have learned:

Slave sizes can be 35, 34, 31 and 30mm. (my bikes are all 30mm).

Later bikes around 82 and newer are all 30mm.

Later bikes can also sometimes be 31mm.

The 31 and 30 use different size O-rings.

The 31 and 30 use the same size O-ring.

Don't use an imperial size O-ring as it will leak.

The imperial size O-ring is OK.

For a 30 mm piston the O-ring size is:

3.0 x 30

3.5 x 30

3.0 x 31

3.5 x 31

3.53 x 29.75

So what size is correct? I am hoping it is 3.53 x 29.75 as that in inches is .139" x 1.171" which would be the exact size of a 217 O-ring which is available locally in EPDM.

HELP!


Also while on the topic of O-rings, the one that seals the plastic brake and clutch master cylinder reservoir, I have been told is a 126 or maybe a 127 or 128 or 129 size? The 127 looks like it is the one?
 
I am also confused but I have a set of different O Rigs for the clutch slave and whenever one leaks one of the set will fit- but confusing issue...
 
I see your in the US. If it can't be figured out without dimantaling and youwant go keep riding for now why  dont you just get Wolfgang to send you the size(s) it may be. Then once you have them you can dismantle the slave cylinder  and pick the right new one at that time.
 
No idea what a 217 o-ring equates to, but suitable sizes for 30 and 31mm slaves are 29,75 x 3,53 and 31,34 x 3,53mm respectively.  Generic sizes that should be available at any half-decently stocked o-ring supplier.

piet
 
If you are in the US , use McMaster Carr, you can get an orange kit from them on the link below or brings individually, depending where you are they have overnight shipping.

If only we had them in Europe !


https://www.mcmaster.com/o-ring-kit
 
You posted on 2 July -
Wolfgang takes 10 days to get parts to me and would like to find some local this Monday.
Click to expand...

How much pain could have been avoided!  >:D  Suspect the issue is USPS rather than Wolfgang - stuff from him arrives in the UK in 5 days or so.

To avoid anyone looking through this thread picking up the wrong info, the following statements are NOT true

The 31 and 30 use the same size O-ring.

For a 30 mm piston the O-ring size is:

3.0 x 31

3.5 x 31


 
All my Lavs have cables, so it's not a subject I think about, but would 'Quad' seals be useful in this application?

Also knows as X ring seals.

I think someone out there in Laverda land should give them a trial. I would, if I had such a bike. If someone wants to loan me a shiny black Corsa for a 2 year long distance trial, that would be most welcome.

Here are the very basics...
https://www.applerubber.com/hot-topics-for-engineers/what-you-need-to-know-about-dynamic-seal-applications/

 
OK, now that I know the size, thanks Piet.

3.53 x 29.75 for the 30mm and 3.53 x 31.34 for the 31mm do not seem to be available in the US made out of EPDM.  But if we convert these dimension to inches we get .139" x 1.171" and .139" x 1.234" which are the exact same size as 217 and 218 O-Rings which are available locally and cheap.


https://www.mcmaster.com/1289N229/

https://www.mcmaster.com/1289N23/
 
you have 30 mm as the piston size
you need 30 x 3.5  "O" ring,  it must be EPDM to withstand brake fluid (its 37 OD if you cant do the maths)

I have used the imperial (BS) sizes (29.75 etc) and they work for a while but leak fairly quickly.

If you were local I would send you one in the post FOC.

CLEM
 
Clem,

You say the correct size is 3.5 x 30 and not to use the size Piet says to use (3.53 x 29.75). So now I am back where I started in not knowing what size to order.

It looks like my only option is to wait 10 days for Wolfgang to send me some.

Bruce
 
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