Modern Vespa

A few months back I rebuilt my factory Cosa II clutch with new plates, pressure plate, bushings, and push rod and it seemed fine... until a few days ago.

I started it up in N, pulled the clutch, went to put into 1st and the engine immediately stalled. Puzzled, I restarted it and it did the same thing. Annoyance and alarm setting in, I felt the clutch lever and it seemed completely normal. The same free play was in the lever and the spring tension to pull it all the way felt normal.

Pulling the clutch cover I saw nothing abnormal. Pulling the clutch and I saw nothing abnormal. With the clutch out I tested the gear selector while turning the hub and everything seemed normal.

I pulled the clutch apart, the plates were wet with oil and I could see nothing abnormal, so I removed all the springs and put it back together and could not believe how difficult it was to turn the plates by hand. It was like they were glued together.

I went digging in my garage trash can for all the parts I'd previously thrown away (fortunately I don't empty the garage bin very often) and compared all the new parts with the old. There were no dimensional differences. The 2 stacks of plates were the same thickness, 18mm.

So, I re-oiled and reinstalled the old plates and with the springs out it was not difficult to turn the plates by hand.

I have a set of Surflex plates on the way but have absolutely no idea what the deal is with these plates. They want to stick together now like glue.

One thing that was different about this build was that I used dimpled steels this time, but I don't know how that would make anything worse.

I'm just sharing this story for others. I suspect the cork material on the plates I installed must've been defective.

(I know what some of you are thinking .... "Why don't you just use Honda plates?" I'm asking that myself. That may be in the near future).

Have you checked the new steels (or corks for that matter) for warp?

I had the same, well opposite, thing happen to me with 2 rebuilt engines, a T5 and a 200, with refurbished cosa clutches. Except that mine stuck from the beginning, even though the cork plates had been soaked overnight (surflex plates as well). Clutches disassembled, oil laid down thick on each plate with my finger, plates reassembled: the one I started up right away worked immediately; the other one having to wait for a tire change was started a week later > same problem > clutch rebuild with oil spread with my fingers > engine started immediately after: success.

It seems the only specific difference between sticky clutches and working ones was the time left between rebuild and actual use. If left for a few days without being used, they stuck; if used immediately, they worked. That was a few years ago, and they've been working fine since..

Dunno why a working clutch would start sticking after having worked normally, but I thought I'd offer my experience with an alternate series of events for reference.

Just installed new Surflex plates and this time didn't soak them overnight but instead just squirted oil on each layer while assembling.

If they swell up any I'll have to readjust.

With springs out, I can turn plates by hand now without much trouble.

Problems resolved.

Weird issue. I wonder if there's some reaction going on between the gear oil and whatever glue or binding material being used in the cork?

You checked that all the plates were perfectly flat?

Yes. They want to stick together. The surface drag is very high, like tires on a road.

So the new dimpled steels work fine w/ new 'nonsticky' corks?

So far, just perfect. If it changes, I'll let everyone know and try to think of something else.