RGS clutch slave cylinder

andrew112_uk

andrew112_uk

Senior member
I could do with some help with fitting a new O ring please.

Looking for a replacement from Motalia, I did not know if it was 3.0mm or 3.5mm so ordered both. I removed the old one which looked hard and perished and the
3.5mm seemed right. I cleaned it all up and the piston and bore look fine to me.

But it leakes....a lot. Even with the casing sitting on a box with no load, it weeps a lot. I've checked and the new O ring is seated OK...just
seems a bit of a loose fit against the piston.

Does it need to bed in or soak in brake fluid to seal?

Grateful for any advice. Andrew
 
3.0 and 3.5mm? Thickness?

What about diameter? There's more than one used in Laverda hydraulic clutches.
 
In the catalogue it just said RGS clutch piston o ring 3.0mm and the same with 3.5mm. There was no choice
of diameter but both were the same when I got them out but different thickness. Looked the same diameter as the old one and
laying the old on the new, I would say they are the same diameter.
 
I had to state diameter when ordering.
Can't remember, either 30 vs 31, or 31 vs 32mm.

If it still leaks then you still have a problem that the seal you bought didn't fix.
Is the piston undamaged? Walls of the cylinder?
Crud in the 'o' ring groove?
 
Thanks Grant.  I just remembered I took a pic. Looking at the old one... It's shaped more like a seal than an o ring if you get my drift. I think it is a different profile and thicker. I'm no expert but I suspect the new seal is not good.
 

Attachments

  • rsz_p5250009.jpg
    rsz_p5250009.jpg
    80.9 KB · Views: 32
http://www.instandhaltung24.com/shop/product_info.php?info=p39535_O-Ring-EPDM-29-75-x-3-53.html&XTCsid=lqpr755vai4e78nkl9o1m62mr3
 
As Cape has just stated you need an EPDM rubber 'O' ring, not Viton or Buna.
Not many 'O' Ring materials are compatible with Dot 3-4 brake fluid.

I got my 'O' rings from Wolfgang for my Jota 120, I have just measured a new clutch slave piston - 30.00mm O/D.
The 'O' ring he sent me is 3.5mm Dia across the segment, and has one white dot, two yellow - I strongly suspect EPDM Rubber.
 
Andrew understand you have cleaned the piston and verified that no scoring... you also need to make sure that the groove in the cover where the seal sits is clean as if there is crud in there it may not be letting the oring sit correctly and can leak round the back. !
 
You need the same EPDM material in any hose used for remote  brake masters as well. Its mainly used in the food handling and chemical industry.
I discovered that after using the wrong hose that weeped brake fluid. These hoses are available but pricey.
 
andrew_uk said:
Looking at the old one... It's shaped more like a seal than an o ring if you get my drift. I think it is a different profile and thicker. I'm no expert but I suspect the new seal is not good.
Click to expand...

I suspect it's the old seal that's not good. The old one is most likely thicker and square in section because a previous owner installed a Nitrile (aka Buna) o-ring that's not compatible with brake fluid. It's been in a square groove for years, and would have swollen and hardened into that shape. It should be a normal round section o-ring.

PS. There are two different diameter slave cylinders used on Laverdas, as you may have gathered from the previous posts. Measure yours before ordering.
 
Dellortoman said:
PS. There are two different diameter slave cylinders used on Laverdas, as you may have gathered from the previous posts. Measure yours before ordering.
Click to expand...

Same o-ring for both the 30 and 31mm pistons...

piet
 
Thank you all for the advice. I've ordered an o ring from Slaters and will try that out.

The piston looks great and the bore and recess are clean. Fingers crossed!
 
It was the seal.  The one Slaters supplied is thicker and the piston took a lot of pressure before it popped into place.

All sorted now  :) MOT booked for Monday and hopefully all set for Summer.  8)

If anyone reads this thread because they are going to replace the seal in the UK, I would advise against ordering it from Motalia and recommend you order
it from Slaters. I'm sure they were just having a bad day but the clutch line Motalia sent was incorrect and had to be returned and the correct one sent.  And the
bleed nipple that arrived was actually a brake caliper bleed nipple which is a bit too long but works.

Thanks everyone for your advice.  Andrew
 
You must log in or register to reply here.
Back
Top