My long held (JADED) view of these devices was re-visited recently as starting was becoming more of a miss or hit affair than is acceptable in my Otter (which OTHERWISE) behaves impeccably, (unlike the owner)
Upon huge illuminations in relative dry and 5 deg C I dismantled and viewed with intense dislike and close scrutiny.
I found the small rod which pulls the carb choke on - to be TOTALLY seized inside the hole into which it is held. The First photo shows the return spring disengaged, and the rod pulled out for clarity.
The second Photo shows rod pushed into choke activation hole, and flip over clip engaging the rod to prevent the rod sliding out. Copper grease has been used to seal the orifice, and will be regularly wiped with Copper grease from now on. The rod needed long persuasion to remove from the hole into which it was seized due to corrosion. The wire rod was cleaned, and scraped, then polished with wet/dry and liberally coated in lubricant.
Currently operation of the electric choke is nothing short of astonishing, i.e. it CLACKS open, then off in a most agreeable and staccato way.
I found the engine would either NOT start (i.e. choke was off still) OR--- it would start then slowly stop due to choke being ON---- and not switching off.
This fault was
A) invisible
B) and the size of 1.35mms!
IE it was not surprising its taken me Soooooo long to recognise and so little time to rectify.
This easy fix wends its merry way to you all so we may start 2019 on a big upper!!!!!