cosa clutch

Hi can the 21 tooth cog on a cosa clutch be replaced with a 20 cog i see sip sell a 20 cog in there catalogue they say it is for px125 not the t5 which i have. thanks

Thanks i have put t5 clutch back in will do a road test later

hi whent for a ride seems to pull more top end not so good then whent from 125 main jet to 122 top end seemed a little better where i live there are not a lot of good roads to give it a good blast if you get a good straight a bloody car pull out in front of you + no wind to day to see how it pulls into the wind. will have a go tomorrow to work clutch not as smouth as cosa probaly put cosa back in ready for mersea rally on friday.


thank you to let me know.
I can understand. I had the same problem. To fully use this short gear the engine should be capable of rev. higher.
For this reason for my T5 I end up with a set up with longer ratio and a better mid range pull at the expenses of some high rpm power.
My T5 set up :
PM exhaust
Malossi kit
Malossi reed
Keihin PWK 28

This I found was the best all round compromise.
It took me a lot of trying… (tried 5 exhausts, two crankshafts, reed and not reed, 3carbs…)


Just to let you know i have put the 21 tooth cosa back in not enough top end with the 20 tooth clutch the cosa was all right just wanted to see what the standard was like as i put the kit and cosa in together.


yes, you can use 20 tooth from latest px125(My) 8 springs clutch.
Not from ealier px 125.


…it is a pleasure.

just let me know how if it is better this way with yor scorpion exhaust.



strange you find the clutch not as smooth as Cosa.
I think it is more due to the feeling that you get more power stress to the primary.

I hope you can set up the engine the way you like.
maybe like me you don’tI liked like Scorpion exhaust with T5 kits.

In my T5 Malossi I end up liking PM. (gearing 21/68 or 20/6[H]
And the second exhausts I liked was Sito plus (21/6[H]…yes less power of course but good drivebility… the problem is that we want both !!but a vespa is not a 4cylinder engine and it doesn’t have 600cc.
It took me a while to accept it ! Always trying trying… and spending money.

I didn’t like the 20/68 + either Taffspeed or Scorpion exhausts.
I could never managed to make the engine work the way I wanted with this last two.

My favorite carb Keihin PWK made also a big difference over the dell’orto. Everything better, more power, better spread, smoother, easier to adjust.

Mikuni tmx also much better then PHBH.

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