#55 massey plow? ?

[Sheepdr]

I have a # 55 massey Ferguson turn over plow. I cannot get the trip chain to return. I replaced the spring and cleaned it good. I couldn't get it to come off to do a real good job. Was afraid to force it to hard. I don't know what's in there. The chain will return sometimes, I forgot to add.
Can anyone tell me if there is a trick to getting the chain guide off and also how tight should the spring be.