Tuning vs jets.

Hello everyone !!
Iam building an P150X engine with this setup.
Polini 177cc kit, Si24 carb, mazzuccelli racing crank,leovince exhaust. What size of jet can i start with ?

Thanx in advance.

try a 125 main jet first, but you may need to go down to a 118, or up to a 130. Retard the timing all the way.

Hello !
Ok so i will buy a 130,128,125,122 jet and if i am correct
the SI24 carb is standard with 120(i read it somwhere on this board)
Then i have enough jets to test with.
Thanx very much.


When you are retarding the time?

… the time for Polini is 19. It works perfectly with this but it could sligthly change according to the exhaust or engine.
Before getting there if you are not sure of your carb setting go 17 or 18 so the hot gases will flow out better to the exhaust the cylinder will be cooler and when you are sure you have the right main go to 19.



if it is the first time you set your carb I think you will find it easier starting from the bigger jet you are going to buy and then going leaner so you will have a dirrect better or worse comparison.