Hi Jamie, The premier carb looks similar to original. However, there are many differences when you examine them closely. The 2 small holes on throat floor are larger. Bowl is built differently. Float level on premier is not .080" below gasket surface. It is just above & parallel with gasket surface. However the actual liquid level remains unchanged should you test with manometer should you have one.
Sellers often sell what they have, not what you had. Many sell a "ready to tune" carb. See AMAL
web site for details.
As was stated the old pilot jet was .017. However the new Premier seems to do much better with .019. As was stated .017 has 2 rings, .019 has 3 rings machined into snout of jet. At the same time you have jets out. Remove drain plug in bowl & shoot some carb cleaner spray into the bore where jet goes. Let the cleaner flush back any dirt, casting flash back into bowl & out drain. Grease the jet o-ring, Helps assembly. They can cut or tear. Deburr bore edge if needed. Flush jet also.
I've worked with several Premiers now. I find the factory does a good job setting the jets. Needle clip you decide & set when you install cable. The main jet, slide is a crap shoot as it depended on how seller ordered carb from AMAL
If the idle screw is too deep like 1/2 turn it skews air flow through idle bore & often causes odd things to happen when bike is warmed up as well. Especially at lower speeds & stop signs, stop lights. The mixture cannot be made ideal in all situations.
Removing choke won't make difference one way or the other since you blocked the cable holes. It will not effect actual starting much, but choke helps you to use more throttle without hesitating during warm up.
Velocity stacks with screens can dramatically alter air flow. So expect to have to tune your new carbs. If bike ran good on old carbs. You may want to examine old jets & slides (except pilot jet), clip position. Start there.
Bushmans guide is good. John Healy's is good also. Maybe better. IN EVERY CASE mark your grip in 1/8s. Critical to know where the slide is.https://static1.squarespace.com/sta...2/1481956877861/Amal+MK2+Carb+Manual.pdf
Print & take in pocket. Try to find a decided road test to see how bike runs in all conditions. Use same road test during tuning so you can feel changes more readily.
Also verify battery
voltage & charging system are good. Low voltage will make bike run oddly.