A good source for information on these carbs is here
http://zenithcarb.co.uk/technical/
They also sell the service and overhaul kits, very reasonable too which is what i like.
Good exploded views here
http://www.marineengine.com/parts/te...ra_18-7085.pdf
To buy the correct overhaul kit you need to determine the correct type/model of carb is it a 150 CD or CDSE, this info is stamped on the metal tag attached to the carb top but alas my carbs are missing this vital piece of info so i have done a little research and found a good description between a CD and CDSE at
https://groups.yahoo.com/neo/groups/...ns/topics/7790
This guy says the CD carb does not have the "By pass valve - Throttle" item 15 on the diagram, if the By pass valve is fitted then its a CDSE carb also the "Valve Assy - Starting" is fitted to 1 CD carb and both carbs on the CDSE twin carb set up.
I found this on tunning the CD carbs
http://p38arover.com/misc_files/Tuni...g_CD_Carbs.pdf
Hope this helps and makes life a little easier.