Briggs & Stratton Quantum - governor spring doesn't move butterfly valve

philduff

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  • / Briggs & Stratton Quantum - governor spring doesn't move butterfly valve
hi all,

Hope this message finds you well.
I have an issue with my lawn mower; it starts, but the engine runs at high revs and moving the throttle doesn't change anything on the reving.
I'm not a mechanic and don't have experience working on engines; but after doing some closer investigation it looks like the butterfly-valve doesn't move at all when moving the throttle-lever. There is more tension on the governor spring, but nothing happens to the valve.
i can move the valve with a screwdriver so it is not blocked/stuck; however it does take a little bit of "effort" to move it. It doesn't take a whole lot of effort to move it; but I feel it is more than the added tension on the spring when changing the throttle-lever position ... (hope this makes sense?). Should the valve move very fluently/easy? Should I spray it with WD40 or something like that? Or Should I clean it with something?

On some engines I can see that the are 2 springs controlling this valve, but it appears that on the Briggs & Stratton Quantum there's only 1. (checked the parts-manual and couldn't find anything in the documentation referring to a 2nd spring)

I've attached 2 pictures, one where the throttle lever is in "stop"-position, and the other one in the "full throttle"-position.

Engine model type: 12H802-1966

Thanks in advance for any help!

Best regards,
Phil
 

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StarTech

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  • / Briggs & Stratton Quantum - governor spring doesn't move butterfly valve
The spring doing it job of holding throttle vane at max opening while the engine not running.

Now if the throttle vane is hard to rotate then carburetor needs to come off and the throttle assembly removed. Usually with these plastic shafts tends to swell and need a little filing so they don't bind in the carburetor. I just did a similar job on a larger engine where the plastic choke was binding because of this swelling of plastic.
 

philduff

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  • / Briggs & Stratton Quantum - governor spring doesn't move butterfly valve
Thanks for the feedback StarTech.
I'm not afraid to get my hands dirty, but I'm a newbie when it comes to engines. Is it difficult to remove the carburetor & throttle assembly & file the shaft?)
 

Superpro9

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  • / Briggs & Stratton Quantum - governor spring doesn't move butterfly valve
hi all,

Hope this message finds you well.
I have an issue with my lawn mower; it starts, but the engine runs at high revs and moving the throttle doesn't change anything on the reving.
I'm not a mechanic and don't have experience working on engines; but after doing some closer investigation it looks like the butterfly-valve doesn't move at all when moving the throttle-lever. There is more tension on the governor spring, but nothing happens to the valve.
i can move the valve with a screwdriver so it is not blocked/stuck; however it does take a little bit of "effort" to move it. It doesn't take a whole lot of effort to move it; but I feel it is more than the added tension on the spring when changing the throttle-lever position ... (hope this makes sense?). Should the valve move very fluently/easy? Should I spray it with WD40 or something like that? Or Should I clean it with something?

On some engines I can see that the are 2 springs controlling this valve, but it appears that on the Briggs & Stratton Quantum there's only 1. (checked the parts-manual and couldn't find anything in the documentation referring to a 2nd spring)

I've attached 2 pictures, one where the throttle lever is in "stop"-position, and the other one in the "full throttle"-position.

Engine model type: 12H802-1966

Thanks in advance for any help!

Best regards,
Phil
Hey Phil, I just fixed my Briggs and S mower today with a seemingly familiar issue. The fact your butterfly valve is in the same spot gets my spidey sense going. It should, as you ask, move quite freely like a feather in the wind. It appears stuck in the open position so hence the fast run. Take all the springs off, see if that matters with a touch back and forth movement. If that doesn’t help then it could be something in the actual butterfly valve or something blocking the governor blade from rotating back. So take off the metal bar that links the valve to the governor flap.
It’s air flow for sure and don’t be intimidated lol. You are smarter than the parts and will win.
 
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