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Can someone explain how the autochoke on this engine should work?

The engine wont run unless I hold a lever behind the muffler back towards the mower handle.
The lever has a linkage across to the carburetor with a spring or two that (I think) are supposed to open & close the choke.
The model number is 126T02-1347-B1, the mower is a Craftsman.

What does the lever behind the muffler do & when is it supposed to be forward & back? I'm guessing the heat from the muffler is supposed to affect it & move it somehow?
Maybe one of the two springs are stretched ?

Thanks for any help
BT.

The heat sensor behind the muffler which you are talking about just holds the choke open for a warm restart. there is a air vane arm under the blower housing, that opens the choke as soon as the engine starts. that system has been an ongoing intermittent problem with some mowers. Some people never have a problem, and others can't seem to fix it.

Thanks for the response, Ilengine -

What position should the heat sensor normally be in - forward or back?
The spring mechanism that controls it doesnt seem to have a lot of strength, its pretty loose & I'm thinking maybe thats the problem.

Should it be pointing back to the rear of the mower when cold & then pulled forward when it starts?


BT

If you look closely at the black plastic air vane arm you will see marks in both directions. 3&9 o'clock posits and 6$12 o'clock positions. The silver thermostatic arm should be adjusted so that it is between these marks. As the engine heats up the silver arm should push the black arm forward, opening the chock. The spring by the carb is not a strong one and should allow the air vane to move very freely. If you start the engine, with it adjusted properly, you should see the chock open. If it does not open, you will need to replace the thermostatic control. You don't give us the code number of the engine, but some of the Briggs engines have a three year garanty to start warranty. Hope you can understand what I am trying to say.

Thanks Rivet - thats very clear.

I think the serial number on the engine is 09041758.

I'll check the thermostat & the black plastic vane arm - do I need to remove the muffler to do that?
The location where the 2 are connected is under a shroud & not visible without taking something off.

BT

Yes you have to remove the shroud to check the adjustment. If it is not opening the chock properly after you adjust, you have to remove the muffler to replace the thermostatic control. It is out of warranty.

I am not sure if my problem is related, but it seems to be related to the air vane arm. I put a new spring on thinking the old one was worn out. The auto choke does not seem to be running correctly. When I put pressure on the air vane arm the engine starts running correctly and when I let go it starts chugging and shuts off. Check out the video and I would appreciate any help you can offer.

Can't get the video to play, just post a picture idicating the spring you replaced.

Here is the picture of the spring and the part #.

Sorry, I wanted to see how you had that spring installed. Did you review post #4?