I am thinking about trying out a slightly larger main jet on my 850.
I have changed from manifold to headers and also made a new air intake with hi-flow filter.

Can anyone help me with the standard main jet size for my carb?
It is a 1970 Fiat 850 (843cc).
Here are som photos of the carb:

Hopefully the attached will help you. Let me know if I can help you in anyway.

Be interested in your results, you going after a little more pep in its step?
I have been told they can be a nasty little carb. I just clean the jets and leave the rest alone.

Yes, im looking for just a little more pep and maby getting it to run a bit smoother.

I don't think you'll get anymore out of it on the performance side without looking at airbreather, exhaust and an electronic ignition. The latter is something I going to look at purely to bet rid of problem items ie points and condenser but that said they have given little hassle so it's not something on the immediate list.

I recently fitted a different exhaust, keeping the original manifold and while it is restrictive with the dual pipes it does clear its throat quicker. Also sounds meatier