Project Vento has begun: help wanted.

[cooperplace]

OK, here's the problem. I reassemble the rear m/cyl, and then under spring pressure the piston pops out again. In the photo below there's a piston, a seal with a lip on it, a thin metal ring that fits around the outside of the lip seal, and a washer that goes over the top. Following the instructions in:

http://www.laverdamania.net/Repair%20Gu ... Master.pdf

I assemble onto the piston the lip seal, thin metal ring, and washer, and use a metal rod to tap the whole into the m/cyl. It goes in and the thin metal ring sticks in an indentation in the bore. So far so good. But when I take my metal rod out, the spring forces the piston back out, taking washer and lip seal, but leaving the thin metal ring in the bore. In the above instructions it says "piston should stay in bore" but it doesn't. I'm fairly sure I have the lip seal+ thin metal ring oriented to each other correctly. To get another lip seal I need to buy another kit, so it's another $25 + shipping + 1 week. And if I'm doing something wrong I'll screw that one up too. Any thoughts?

13mm.M.cyl.piston.kit.JPG

[Duccout]

I'm not sure that is the correct seal kit, there is no metal sleeve that has to driven in in the picture, you know the sleeve that you drove out when you removed the old piston. You may be able to reuse the old sleeve if everything else fits OK, you tap it into the cylinder with a short length of (preferably plastic) tubing.

[Duccout]

Having looked at the pictures in the link, I'm not sure now, it is different to the front cylinder that I worked on years ago, and looks like it just uses the metal washer to hold the piston in place.

[Jon Pegler]

It looks like the right kit, but I'm not sure that you are assembling it correctly.
The plain washer goes over the end of the piston first, followed by the rubber and finally the thin ring with it's sharp side outermost.
Make sure that the rubber is the correct way round, largest diameter goes onto the piston first. next to the plain washer, so that the thin ring can sit in the recess facing outwards.
As Colin says, you need a thin tube to tap the thin ring in squarely.
If the thin ring has been in once it may not hold properly a second time or may need carefully flaring out slightly to help it grip in the bore.

Jon

[cooperplace]

Below is the m/cylinder with the new parts on the left and the old on the right. Identical. I reassembled it, and this time the piston stayed in the m/cylinder, so I mounted it on the bike. But I know that if I push that piston in & out, the seal will just pop. So my concern is that when riding it the same will happen.

rear brake m.cyl291120a.jpg

[Duccout]

I've just re-read your earlier post and I'm wondering how the washer and seal can come back out leaving the thin ring in the bore, unless Jon is right and you are assembling it incorrectly? The washer and seal look too big to pass through the thin ring, so how do they manage it?

[cooperplace]

aah, I think I'm putting them on in the wrong order. I'm putting on lip seal, then thin metal ring, then washer. So only the flexible rubber seal is being forced past the thin metal ring. But the laverdamania instructions say to put them on in the order of washer, lip seal, then thin metal ring. When the old ones came out they were so crud-embedded it wasn't possible to tell what was what until I'd cleaned them a bit, by which time I'd lost the order.

In the morning I'll try them in the hopefully correct order. Thank you for your excellent suggestion.

[Ventodue]

But the laverdamania instructions say to put them on in the order of washer, lip seal, then thin metal ring.

As did Jon, just now ...

"The plain washer goes over the end of the piston first, followed by the rubber and finally the thin ring with it's sharp side outermost".

Also as Jon warned, be careful with the retainer ring, Peter. It's intended for a once-only installation ... . Let's just hope you haven't over-stepped the mark.

If you have, and if you're very careful, you can (also as Jon says ... ) try to re-flair them. But always best avoided.

[cooperplace]

What a difference the correct order makes! All is now bliss!

Having worked out what I was doing wrong, I'll buy a new piston & seal kit and put it together properly this time. It is the brakes after all.....

Thank you everyone for excellent advice, very much appreciated.

[cooperplace]

The local Duke mechanic who is working on the engine reports that some clutch plates are warped, and recommends a new clutch; fair enough.
Lacey's site shows a std 250/350 clutch set (£83.50) and an "uprated" clutch, £79.95. The description reads:

"This kit was originally designed for racing use to overcome the problem of the thin 1mm steel plates overheating and distorting. The 2mm plates overcome this problem and this combination is a direct fit in the standard basket. This kit is however equally suitable for road use and can reduce clutch drag dramatically."

Bearing in mind that I won't be racing, nor placing high demand on the clutch, and I'd like it lighter if possible, any recommendations or advice for the clutch would be much appreciated. Thanks.