OK I stripped an old pump this morning to get you all some pics of how to cure this simple but messy problem.......
First pic...remove the tying wire and remove the two nuts on top
2nd pic...remove the nuts and washers and levers from the throttle and strangler shafts
3rd pic...you need to look in and upwards to see where the spring is attached...be very careful as the spring can unhook. (my camera had bother focusing)
4th pic....there are 3 holes on the linkage at each end, this is the front end of the spring and my 135 type had the pin to connect the spring in the top hole.
5th pic...and the spring in the hole closest to the shaft on the back/lever end.
Carefully lower the lid back on to the pump making sure the stop linkage is hooked in correctly( Front shaft) Make sure you get a new gasket for the pump body to lid and new sealing washers for the fixing studs and 4 new 'O' rings (2 per shaft) 6th pic. That is about the best I can do for you from this side of the Atlantic! Sam