Remove the side cover (2-4mm Allen)
The control rack is stuck..
U must be VERY CAREFUL.,
EVERYTHING is made of pot metal and breaks easily.!!
When was the last time u put oil in it.?
U might get lucky spraying it down with some penetrating oil and letting it sit for a day..
I just got done w one and had to replace the camshaft & bearings..rollers and springs..
I can rebuild it, several hundred less than buying new..