33mm FCR carbs run better without the accellerator pump because the pump causes momentary flooding when shifting normally through the gears.   You can replace it with a "primer choke" similar to the Amal tickler (but no gas leaks).   Simply push it down once or twice the first time you start it and you're good.  You can reinstall the original accellerator linkage if you want to go back.  Add this to your purchase of JS 33mm FCR carbs to get the upgrade.