Tuned px200 destroying clutches in 100 metres

 I am a Classic Scooter mechanic in Melbourne, Australia. I have put this problem to the other Vespa dudes in Australia. Now it goes out to you.

I have been battling with a tuned PX destroying clutches for far too long.

I am absolutely stumped. In desperation I am putting this problem out to the great minds of scootering. Here is the timeline. If I have missed something Stupid then good. Tell me. I have ridden this scooter for 100 metres and it has hammered its clutch to bits so I cannot blame the rider, the Horsepower or the fact that cosa clutches are weak.

I have another 24HPO at the wheel px here that has has an off the shelf banded cosa on for 8000kms.

My next step is to get new cases and start again.

It’s a shame as it pulls 20horses between clutches. (I have a dyno)


2nd hand px200 (2004) done 18000 kms

Pinasco kit goes on with mild pinasco pipe

Rides for another 4000kms

Vespatronic (1.5kg) installed

Rides for approx another 1000 km

Rivets shear on cosa clutch, two go into motor

Split cases and remove rivets (crux/seals)

New banded and welded clutch (newfren)

200 kms later Clutch blows its retaining ring

On inspection the clutch cork tabs had hammered into basket completely destroying it .

Pulled motor down and rebuilt cush gear plus installed JL right hander.

200ks later another clutch destroyed - Pulled motor down and installed LS crank, new bearings seals crux etc. Matched ports.

installed billet clutch gave up getting it to work without grabbing and used 7 spring px clutch.

Chewed up in 500metres - Pulled motor down and replaced drive shaft (axle), several gears, ALL bearings etc. NEW genuine stock cosa clutch.

50-60km corks show signs of wear (;ike 10-15000 kms) and basket is beginning to show damage.

Replace and continue carb tuning.

Clutch retaining ring blows out in neutral while revving. Dismantling shown demolition of corks, plates and basket. Corks appear a little dry but not burnt in any way.

THINGS DONE IN HOPE WITHOUT A RESULT – changed crank, bearings, drive shaft, 5 clutches, rebuilt cush gear, pressure plates, levering plunger arm, plunger, gears

THINGS NOT DONE – return to standard flywheel, spacer cog behind clutch, engine cases.


Thanks for reading

let me know if you have come across this before.





returned to standard flywheel, put in a STOCK cosa clutch and it was fine after 400kms.

the stock clutch was just because I had one handy. Once I was confident the problem was gone I returned to the welded and banded style.


Hi Australia!


with our newest Clutch you will never have a prob again- not with 40 HP! have a look here:











This is an old thread so I’m writing this for other people.

The Cosa clutch is an expensive design that wears out fast but is much better at controlling big power.
I always found the standard PX clutch with heavy springs disgusting to use at the lever, killed cables, and often slipped anyway.
The worst wear is actually in this part 15985400 and MUST be replaced with corks every time IMO. This is the snowball that creates the avalanche.

Lightweight flywheel means crank is accelerating/decelerating violently at idle. The corks rattle themselves like crazy in the basket and the rivets will work loose. The corks also hammer into the sides of the basket which means they won’t release properly after a while. With the heavy flywheel it is much smoother and kinder. The more power you make, the heavier the flywheel you need on a single (without a balance shaft) !

Other mistake people make is to stand next to the scoot when there mates are there and rev the guts out of the motor because it picks up speed very fast and sounds really nice and angry. You can do this on a motorbike because the clutch isn’t doing crank speed, but on a vespa PX when your engine is doing 9000 rpm your clutch is doing 9000 rpm. With a light PK/Varitronic flywheel the clutch accelerates so hard it flexes and the retaining clip will be thrown out and then the clutch causes the ‚explosion‘ as it crashes into the gearbox ruining everything.

If you already own a light flywheel and you are convinced by looking at forum graphs that this is one of the secrets to your success, then try to resist revving it in neutral. I think far fewer people have a clutch explode accelerating hard up the road than revving it in their driveway. The new part 93245000 looks like how the factory should have always done it !

All the best fellow tuners !

Back to basics.

Never shagged a clutch that bad as all above.

Hi Derek !


If you got an engine over 20 HP i recommend a special clutch basket, please have a look on item
93245000 (for cosa clutch with the small springs) or 93270000 (for the old px clutch with 7 big springs).


I guess that this basket is strong enough to go over 30 HP.



Hey Derek, Brett from Brisbane have same problem mate. px210 mallossi daily ride, have wide wheel kit on back thought maybe that  was problem. I have had 5 clutches in scooter so far. Each time clutch rivets gone. have tried new style cluch baskets and old , carbon plates different spring combinations. still same things happen. have tried to lose as much weight as possible. thought that might cure it. as soon as it gets really hot up here, has that sickening sound. if you get a solution please let me know.

 cheers mate


Hi, if you don't use a reinforcing ring, the clutch will invariably explode...