Fixed!
Two issues: The main one (as suggested by @decca and @jimbo84) is that the spring on the bottom lever wasn't tight enough. Angle grinder to lop 1/4 off it it's now wanting to stay up unless forced down by the saw mechanism:
View attachment 224523
(the spring on the left)
The other issue was that the lever that pushes down on that handle was wound all the way down, so the saw could never disengage. Removed, cleaned, refitted and adjusted and we're good to go!
View attachment 224524
Thanks for everyone's help![]()
Glad you've got it sorted

altered it to contactor and limit switch and changed the pulley that's before cleaning and painting as it was fully refurbished 25 years ago