Walk behind Mower starts but quits unless manually hold throttle - linkages good

[PTClyde]

Greetings. I have a Craftsman Model 917.385320 walk-behind mower. (4.5 hp, 22" cut).
It was running fine but now it starts and then quits. The only way to keep it running is to manually throttle it.
(there is no manual throttle control - there is only a dead-man's bar)

When I manually manipulate the head of the throttle shaft it revs up fine.

Any clues? Thanks

 

[Rivets]

I think you should take it to a mechanic. What you are moving is the throttle. It will be hard to help you if you don't know the parts we would be telling you about.

 

[PTClyde]

I just removed & cleaned the entire carburetor and replaced it again. I cleaned the pickup & the screen. I added fresh, clean gasoline (drained all gas out of tank & put in fresh gas) - no joy with any of that. I can get it to start but need to manually throttle it for it to remain running. As soon as I let go of the throttle it dies.

Anyone who can offer some ideas, that would be appreciated.

EDIT:
I think there a governor spring on this unit that perhaps broke / fell off. I didn't see any spring during my recent disassembly, but I am going to risk the $3 and put that on.
I think I remember there being a spring there from my work on this mower a few years ago.

 

[ILENGINE]

I think you are missing the governor spring, so I would get one and try that. May need to readjust the speed after replacing the spring.

Most of the newer mowers don't have an idle circuit in the carb, therefore will not idle or run below a certain engine speed.