Gearing for PX 125 (2004) with Pinasco 177

Hello everybody.

After many research and many thoughts I have decided to install a Pinasco 177 cc Kit on my PX125 (2004), also I have bought a Carb Si 24/24 and a Simonini pipe. I think I know how Jetting and Timing it in the right way.

I am doing half city/half highway

The question then is:
¿ Should I do something with my gearing or the stock one will be ok ? [?[]

Many thaks to all of you

Thank you very much for your reply. Probably I would stay like that and let´s feel it. [:dance1:]

Just one more thing.

What will be approximately the top speed and the cruising speed with this set up ?

Would it change a lot if I change to a longer gearing .

Thanks again for your cooperation.

here you will find how different gearings will influence your speed:


[:dance1:] [:dance1:] [:dance3:]

When you upgear a bike you should be moderate, don’t overdo it.

[:bounce:] [:bounce:] [:bounce:] [:bounce:]

Fail MOT!

Loan an original tire for the test when it comes up. Have also in mind that a 22 teeth clutch means that you must exchange the primary drive and split the engine.

Speed with standard gearing is 100 - 105. You can change the gear ratio with another rear tire.

I’d stay standard.If you ride it and decide it’s too short then change it.

I would change some information about that issue for touristic information about Spain

[:dance1:] [:drink:] [:drink:] [:drink:] [:dance1:]

Anyone interested ?[:D]

Either 21t or 22t. PX125 is 20t. Each extra tooth give approxamately 5% extra gearing.

I have a set up like yours and I enlarged the case transfers (welded aluminum) to match the kit.

I had the 23/65 P200 primary on it. - But cannot withstand head wind at all.

I'd suggest you to get the 22 COGS Cosa clutch cause you don't need to open the cases since it will fit with the 68 gear. ( I measured the std 20 clutch and the SIP 22 and both have the same diameter )

I am now driving with 22/65 and a slightly smaller tire (110/80 10) but the clearence between tooth is way too excesive.  That is why I suggest you not to go further than 22/68.





Hi Tragon,
did you work the transfers and cut the crank?

In affirmative case I’d go for a 23/65 primary and with the 36 cogs fourth gear that you should already have. Riding with longer 1-2 and 3rd gears is more fun!
You might have a problem though with 3rd 4th gear jump (I’m not sure if the Simonini would behave well) and would go back to standard exhaust.

Max speed could be also of 115-120 Km\h


Thanks for all the info.

I have been talking to my mechanic, he is a nice old guy, very experienced with vespa but not really in the tuning side of it [:@]

He told me that he can change my gearing system, but no idea about how would it behave or if would be too long or not. His proposals are going for a 23/64 Malossi, or going for the gearing of the PX200 … He knows how to do it. but does not know how the vespa would behave.

Do you think any of these would be right for my set up ???

Sorry about all these questions…I would love to get all this mechanical charity from you

Great Link. Thank You

Yes or by changing your clutch gear to 21 or 22 tooth. Simmonis make power fairly low down so you should be able to pull higher gearing. As LI Ralph says fitting a 100/90 tyre will upgear by approximately 5% but you must space the wheel away from the clutch cover.


Regarding the 90/100 tyre, in Spain, I would fail the MOT with it ( probably also with the Simonini ). So Probably is better to go for the clutch gear wit more tooth.

¿ Which of the clutch gear available would be OK for my PX ?[:look:]