Pk 50 project. Experts opinion!?

My pk is going through full restoration.

It needs more speed, now it does 55km/t on flat, and barely 30 in any slight hill.

What do you 'vespa experts' in here think of this set? 

-Racing Cylinder D.R. 85cc 
-Gearing 24/72 3.00 cogs
-Exhaust FACO ET3 "Banana"
-Carburetor DELL`ORTO SHBC 19.19 E 

sounds okay?  any tip or suggestions?
and what about valve size for this?  
3,50 tires?

Speak your mind and help revive this beautiful creation!

Thanx a lot

Hi !

I absolutely agree, the PK is amazing! 

I'm not limited, but 85cc is enough for me, I only need a bit more uphill power. 

How do you think the PK would perform with 85cc , 3.00 gearing, 19.19carb , and a banana?

Which jet size would you use?




Come on SIP! I just want to spend some money in your shop... Please answer my questions so that I can purchase the items for my vespa!


jetting is always tricky. i don't think you need to jet up too much, but to be on the safe side, i'd start at around 80 and see how far down you can go. 

i'd suggest a 2.86 gearing... a racing crankshaft might also be an option. but the pk will also run with the setup you have in mind right now...

hey mojo... are you limited cc-wise? why don't you go for the 'real upgrade'? polini 133 etc.

i used to drive a 50cc pk on the road and still have a fully equipped racing pk. some ppl might disagree on that but i think the pk's a lovely model :-)

With the DR 85cc on the last smallframe we setup we did no jet change, but as you are installing a larger inlet manifold and the SHB19/19 and a better pipe you will need to play with the main jet. Around 80, 82 should be fine but depends what jet came with the carb you have you may just need to drill out 0.1mm at a time till you work it out, no 2 setups have come up the same.

You could also install a 102cc these give a bit of zip without changing the crank.

Good luck and report back