Modern Vespa

I have a old, new to me, ET4. It ran when I bought it.

I installed a new fuel tap. It works; if I suck on the vaccum line I get fuel.

I tested with a known working brand new intake manifold and I still get no fuel out of the line.

Does this mean bad compression in the engine because im not getting vaccum to pull the fuel?

The engine turns over with strater fluid

Perhaps here may help?

No vacuum from carb? [FIXED!]#:~:text=If%20you%20are%20not%20getting,at%20the%20head%20and%20carb..

thank you, but ive check the things discussed in this thread

oh ok, if you havent a compression tester then you could try to Remove the plug and place your thumb over the hole, closing it as tightly as you can. Crank the engine. If it blows your thumb of the spark plug hole, chances are there is enough compression for it to start.
Using kick start does it kick easily or do you feel there is compression?
evan quite low compression it would pull some fuel into the carb.

does it run with carb full? pull fuel line of petcock use syringe and fill carb with gas. if you have spark then should atleast fire a bit or run for a minute.

have you checked clearence to valves as this also can cause low compression?