Only running on full choke

Something blocked. When did you last clean the jets?

Are you operating the air slides in the right direction?

Surprising how often this happens. Does nobody read the instructions?!!.

If the carbs haven't been used for a while the pilot jets can become blocked - the only way to clean them properly is to poke a 16g drill through them ( or a single strand of clutch cable), having removed the pilot air screw. Just blowing through with an air jet won't work.
John

The bike that initially confused me most in starting was a BSA M21.  Ignition advance retard lever, air lever that you pulled tight to open air (i.e. normal running) and a decompressor. The saving grace was that it was relatively easy to kick over even if you didn't get the piston positioned just right.  After trying many bikes at the Try a Classic events at the NMM I realised what I really wanted was a twin cylinder bike - much simpler for me to start.

Some BSA singles had tight wire advance.

Probably confuses some people and also retards itself as you ride down the road.

... some Norton singles - the ones which had the inlet cam driven by the exhaust rather than directly from the crankshaft pinion.