If it will only start with a prime (fuel down the carb) it is seriously starving. I suspect that the low speed needle is fully closed, or very nearly so ( the assumption is that you are trying to start with the throttle at a fast idle setting).

Open the low speed jet ~ 1 1/2 turns from fully closed, then open the high speed ~ 2 1/2 turns from closed. That should at least get you on the map, but it will likely be rich. If it still will only start witha prime, open the low speed another 1/2 turn & try again.

The high-speed jet won't come into play in terms of engine tuning & performance until the throttle is ~ 1/2 open, but it is the conduit through which the fuel reaches the carb jet & the low speed needle. The low speed needle restricts & adjusts the flow from the fuel jet in the carb until the transition to high speed operation. The two adjustments are somewhat interactive for final tuning -- but for starting, if either needle is closed too much, you just won't get it going.


When it is running, go to full throttle & adjust the high speed jet until the engine peaks, then back it off until the engine starts to lose revs. Go to idle at let it run there for at least 30 sec -- if it just dies away & stops fairly quickly, it is still a bit lean on the low speed -- adjust it open in 1/4 turn increments until it stays running at idle.

On the other hand, if it starts to stumble & blubber at idle speed & eventually staggers to a stop, it is too rich. Close the low speed needle in 1/4 turn increments until it at least stays running.

That will let you keep it going for the break-in process --- follow your manual for that.