This is a Solex on a 63 Giulia Spider Normale. Carburetor works fine other than choke (starter circuit) not working correctly. I have rebuilt & cleaned everything several times. Engine won't start with choke on. Need to pump accelerator several times with choke off to start engine, once engine is running, if you pull choke out 1/2 way, the idle increases (seems normal?). Go to full choke & it stalls immediately. I have reground the choke valve(disk) and mating surface on carb body flat. Any suggestions of what to try next?