Bandit carb query

[Reddragon]

Got a problem with my B12 revving to 6k on tick over and wont settle down, carbs are BST36 , just stripped cleaned and rebuilt with new o rings and float valves etc , I've done a few checks

1 idle adjuster is backed right off

2 butterflies are all closed 

3 slides move freely up and down 

4 sprayed carb cleaner around, no air leaks as far as I can tell 

5 plugs are black, so its running rich 

6 disconnected all cables and no changes 

I've attached a pic of the carb plunger, theres about 5 mm of it still protruding with the choke off and no cable attached,  so is that normal,  or is something maybe stopping it going fully home 

[Captain Chaos]

On my Mk1 B12 carbs the choke plunger sticks out 7mm in the closed position. 

[Reddragon]

Thanks @Captain Chaos, I've  just measured mine at 6.7mm , so I'm totally baffled as to what's causing it