Modern Vespa

I should have listened to you guys and just got a better clutch (vmc molle) , I've been dicking with this SIP Cosa 2 sport banded clutch grabbing for days, and I'll get back it to it tomorrow to check the slot/turret depth AGAIN but it's pretty disappointing, clutches are simple things and vespas seems to have the touchiest most sensitive ready-to-break-any-mile, keeping my hand on the lever (not that it would work anyway) feeling.


I've got micro adjust levers, new cables, new hardware and the roller thrust bearing which I had to custom make into a +1mm, the cover clears fine , I can adjust till the Kickstart slips etc.


I just now saw a thread mentioning 20mm as the measurement for the turret/slot depth, has this been the fix for clutch dragging? Or do people just give up and go billet?


Also does anybody make an actuator arm thingy that has a better system? Maybe a small roller and adjuster that the cable can go thru instead of just metal on metal action all the time?

I have same clutch and haven't any problems with it(despite weak plates and discs).

Did you check that the baseplate protruding from gear cog?
If there is no difference in height than this spacer can help.

Checked baseplate to cog clearance and it's fine, disassembled the clutch, re-assembled with 4 springs to be able to actuate it easier by hand, took out washer and held it to the cog/ baseplate face and there is obvious clearance and no signs of wear on the cog face where it would make contact, I also made sure that it all spun freely within the basket, re-oiled the plates, put it all back together with all the springs, installed, adjusted via Kickstart method, and like every other time, it seems to be okay at first, ride off down the street and after a but it gets more and more grabby until you can't even get out if gear....I gotta say I'm pretty mechanically inclined, spent many years as a mechanic in the hot rod and marine industry. Never been stumped this easily AND by a scooter lol.

This whole operation worked fine with the stock tiny old style clutch, besides the exploding bit, I thought the Cosa swap would be easy as cupcake!! It's been a nightmare so far.

What does this mean
"the roller thrust bearing which I had to custom make into a +1mm"

There was too much play between the SIP thrust bearing and the face of the clutch, so i added a 1mm brass spacer to the plunger shaft of the thrust assembly.

can't you just adjust the clutch cable 1mm instead?

Sure, but then the clutch arm would reach the end of the throw and still not be able to actuate the clutch all the way, leaving me with no play at the clutch handle, and the plunger partly depressed at all times.

without the 1mm I added there was alot of play before it started actually making contact and depressing the clutch.


I know it's not a diagnoses but it "feels" like there ain't enough travel to fully disengage.

The brass plungers on all of my scooters are partially depressed when the clutch levers are released. I simply adjust my pinch bolt and adjuster nut (down at the clutch arm) to where i like my clutch to engage.

Are you not using a spacer washer Roland link to?

Of course, I can adjust it to zero play which would be obvious, my issue is that no matter how far the clutch is depressed, it still doesn't want to stop dragging.

I am only using the oil pump drive gear as the spacer, is the washer a required part for Cosa clutches? As stated by Roland, the thin washer is implied for use when the cog and baseplate are not correctly aligned.

Explains why you needed to make a spacer

It's always something.... I couldn't even find mention or examples of the washer until today, nor did I see mention of being needed when buying or looking for parts

anything else I had seen in regards to spacers and Cosa clutches was in reference to the spacer and or gear.

Had I known, I would have used it. Would seem beneficial to be included with clutches or at least be a reccomend product, I'll get the washer and try again.

To be honest you absolutely don't need this fancy pressure plate with bearing.
Did you try with standard plate and push rod?
BTW there is DRT plates with +1 and +2 mm higher.

Is it possible that pressure plate touch clutch nut or thread on shaft when clutch is pushed?

Fix_it_with_fire Is your clutch actuating arm new?

If the end that pushes the brass plunger is worn, you're not going to get much movement to disengage the clutch.

roland87 Disappointed... i love my fancy bearing pressure plate...

But honestly, seems like a lot of people have had problems with it... exploding, or coming loose... seems like it doesnt always work.

I'm was read a lot about bearing plates, and I concluded for myself that it is not necessary.
I also had a problem with XL2 Ferodo clutch in my V5B3T engine.
And Cristian "CRIMAZ" Mazelli said that his bearing plate will fix it. I ordered that part but it not helped.
Then I went back to single spring V50 clutch but with Crimaz plate and can't noticed any difference with standard pressure plate.

Have you tried the crimaz 8 spring product? The one that replaces the one spring?

Seems good for mid power engines

There isn't problems with V50 clutch with Polini Wave spring. It have stiff lever, but not a problem for me.
When time has come I'm more inclined to buy VMC Hard Work clutch or Egig One Finger than add some small parts to current clutch.

Lemme start with a really basic question: Why did you install an upgraded clutch in the first place?

Assuming you still have the original clutch, have you tried installing it to see if the issues resolve? If so, maybe you just roll with that.

I have some pretty respectable motors (17-18 HP) that do just fine with a stock seven spring clutch. That thing doesn't get nearly enough credit, IMO.

I also have much much serious motors with BGM Superstrong clutches, which are COSA2 derivatives and cause a lot more of the sorts of issues you're struggling with, so lemme kick out some thoughts and suggestions in the form of questions.

There are lots of good suggestions in here already, but they don't seem to be working for you, so let's stop and reset for a moment. You'd have to ditch your ball bearing pressure plate, or get the one that doesn't have the top hat integrated into it, but Crimaz make a pinion gear plunger set that might work for you.

I tried it in one of my bikes and it didn't press square on the plate, causing off-center contact and rapid failure, which was extremely disappointing, but I put it more on the clutch cover than their design.

So with that glowing endorsement, I'd suggest you go back to basics.

While it seems simple in theory, as you've noted, there's more complexity/ingenuity in the clutch system than one would think. Your issue seems to be that there's not adequate compression range for the clutch itself.

This gives you two options:
1) adjust the height of the clutch to better match the compression range of the cover. This is the route you've taken thus far, adding the millimeter spacer to the pressure plate (which was pretty genius, btw )
2) Increase the compression range by increasing the headset lever travel range or decreasing the clutch arm length. I'd suggest the former, as the latter is going be a lot harder to pull off successfully and will also reduce mechanical advantage and make the clutch stiffer overall.

This leads me to want to see comparative pictures of your old versus new lever. Is it possible that the new lever has less travel than the original?

If so, or even if not, you could also grind back the new lever to add more travel. I had to do that with the front brake on my smallie to work right with the disc brake's master cylinder. Works great and you'd never know it to look.

Alternately, I know you said you have new cables (and pretty much everything else), but...

Are you 100% certain that the clutch cable routing is correct, the outer is the correct length, the ends are fully seated into their housings?

They should naturally tend to seat themselves since the clutch arm provides constant pressure, but can't hurt to check. If you didn't measure the cable length, they are frequently 6-12" too long ("For a Grade A Repair," my ass) and need to be trimmed back for optimal performance

Can you turn the clutch arm easily in the cover when the cover is off the motor? i.e. is there any more resistance than just the spring?

Does the clutch compress and spin more-or-less freely in a clutch compressor tool?

Is the clutch correctly assembled with the plates in the correct sequence and alignment? If yes, how do you know?

Have you considered adding an even thicker base spacer/thrust washer?

Are you certain your existing thrust washer is not worn?

Any of these can cause the sorts of issues you're describing.

it had the weaker 6 spring style which failed on me, I replaced that with another. and when I started this rebuild, this clutch was not looking any better.

I had the same levers as before as well and same cables as before. The only thing I changed this time was inners, clamps, clutch, thrust bearing.



I'm going to install the washer and a new spacer, and see where that gets me.

I know there was problems with the earlier 2 or 3 peice roller thrust setup, this one is pressed into one unit so less likely to explode, I never enjoyed the brass plunger wearing but in retrospect maybe replacing a 2 dollar brass part once Ina while ain't that bad 😂.

Will dissasemble the cover today and check arm for wear, I remember replacing those components 5 or 6 years ago when the clutch first failed on me but it's entirely likely could be worn. If they are ill replace them.

Little update for you guys and gals.

I finally got both the 3.7 mil spacer, and the 1 mm spacer washer, I also got a DRT brass plunger, and an sip Factory Style thrust plate. Got it all installed and everything seems to be working well, have ridden maybe 75 miles so far with no clutch dragging and was able to get out on the open road a bit and get to dialing the engine in.


On that note, the VMC crono kit is superb!! With the 28mm phbh, and 60mm crank, it feels and sounds VERY crisp. And the 23/65 gears feel great too!!


Thank you again to all the fine folks here, I know plenty of us have given up without you guys ❤️ much love

Enjoy your rides!

Alright fellas I'm back woth another clutch problem, this time I sploded' the SIP Cosa 2 sport


Well, more like shredded the tabs clean off the plates ☹️

I'm kindof confused here becuse previously I've blown clutches but it was the basket failing

This time the plates have completely torn the tabs off but the basket is fine


A) I'm a big dummy
B) these plates suck
C) not enough clutch for this engine
D) option a

B, they suck. CR80 plates don't break like that. Each plate will need filing to fit under a ringed basket but will last many years.
https://www.sip-scootershop.com/en/product/clutch-friction-plates-sip-performance-cosa-2-race-clutch-cosa-2_93081400

why are you fucking around with this clutch dude? Get rid of that junk . . . and that is exactly what it is. go- VMC and never look back.

Thanks, gick, just the push I needed to pull the trigger on one 😂

Anybody have them in stock stateside?

Just wanted to say that the VMC clutch I got from gick is operating absolutely beautifully.. Couple hundred miles in And the scoot is feeling and running better than ever.. Truly appreciate everyone on this forum for all the help. This place has kept my old jalopy and my spirits alive!

My (clutch) woes are no more! Until the next fiasco friends

Glad it worked out for you. I bought the same clutch for an engine I will be building soon based on Mr Gick's suggestion.

I got mine from RDV scooter in Italy. No VAT and quick shipping.
https://www.ricambi-v.it/

I don't have your level of experience, but enough that I thought Vespas would be a walk in the park. Nope. Have made many rookie mistakes and been stumped by simple things.

All my years wrenching on everything from boats and cranes and bikes and everything in between, I'm always learning and it's ESPECIALLY the simple things that are most important. The vespa has tested my patience and knowledge every step of the way. It's takes as much if not more knowledge to build a vespa engine correctly as a Detroit deisel or a small block chevy, and I've done a hundred of those

This is so true. Well said. Its deceptively simple, yet there are so many details that if not done properly, will result in poor running, shortened lifespan; or catastrophe. Much care and thought needs to be put into these 'simple' machines.