Briggs and Stratton 190cc throttle not working

[nicknsw]

Hi there.

I have a Briggs and Stratton 190cc 4-stroke push mower. It starts fine, but runs excessively as if the throttle does not work regardless of where the throttle lever is between rabbit and turtle.
So, when the throttle is open the engine runs at 100%, as if the mixture is too rich.
When the throttle is fully closed the engine cuts out, which is what is expected.
However, when the throttle is anywhere in between open and closed it continues to run at 100% (rabbit), there is no varied speed/control from the throttle lever to the engine.
The three images below shows throttle open, halfway, and closed.





Using the above image, when the throttle is halfway or closed, the plastic part marked (2) which controls the valve in the carburetor doesn't move. When the engine is running, either fully open (rabbit) or reduced throttle, and I manually rotate/pivot part (2) it causes the engine to slow and even stop when fully rotated. It's as if the component marked (2) is missing a second governor spring that pulls/pivots the part from left to right as the governor arm moves back (right to left in the pic).
The other parts marked in the picture, includes (1) governor spring attached to the throttle which appears to be correctly placed, and (3) showing the positioning of the throttle mechanism when closed and the engine cuts off - again, this appears to work fine.

Details about the engine below.


It's got me stumped and I would welcome your help. Thank you in advance.

 

[nicknsw]

Anyone?

 

[bertsmobile1]

How the system works
On the end of the rod that the spring is connected to is the governor
The governor pulls the rod backwards to make the engine go slow against the spring that stretches when you set the mower to full speed
So it is a tug-O-war between the spring & the governor.
The faster the engine spins the stronger the governor should be pulling that rod back to slow the engine down .
To check if it is working start the engine, set the control to 1/2 speed then work the throttle plate ( red 2 ) with your finger on the loop that the spring connects to.
The faster the engine spins the stronger the rod should be pulling back against your finger trying to close the throttle.
If not then you have a governor failure .
The numbers on the sticker that you posted are EPA numbers and not the engine number.
The real engine number will be stamped into the engine and on that model should be in the heat shield on top of the muffler .
IT should start with 12 unless you bought it from Bunnings where it could be a cheaper engine .
To access the governor linkages you have to remover the shroud on top of the engine .
Some times crud like twigs can get stuck under the shroud which prevent the governor from working.
That is the Tornado model designed by graduate industrial designers who have zero idea about lawn mowers.
It is pressed from very thin steel and highly prone to failure at the left side handle bar mount
Make sure you keep the bolt tight & keep the space around the mounting plate and the top bend very clean
I scrap around 20 to 30 of them every year and where possible fit the engines to earlier bases that are far stronger

 

[SeniorCitizen]

Is the throttle plate wide open with the engine dead ? It should be .

 

[nicknsw]

Thanks bertsmobile1, appreciate your points. Like the comment about the Tornado designers! I'll go through your steps and post here my findings.

 

[nicknsw]

Is the throttle plate wide open with the engine dead ? It should be .

When you say "throttle plate wide open" is this figure (3) in the diagram, the plate which pivots from being open and closed? THanks for your input.

 

[StarTech]

Either the governor is out adjustment or the governor/oil slinger has failed. Try doing a static governor adjustment to see if this corrects the problem. If it don't then it is time to go in.

 

[SeniorCitizen]

When you say "throttle plate wide open" is this figure (3) in the diagram, the plate which pivots from being open and closed? THanks for your input.

No , #3 may operate it but it's the round disk valve down inside the carburetor throat below the round choke plate . May need a head lamp / flashlight to see it .
At about 5:10 in the vid he shows a throttle plate .

 

[nicknsw]

thank you all for your tips and input. Hopefully, this is one item I can save following the floods. I'll post back here at the weekend after going through each. Appreciate it

 

[nicknsw]

Thank you all for your assistance. I am grateful.
Bunnings model, Victa Tornado. 625 series.

@bertsmobile1, you suggested I check the governor. I did this, as suggested at half throttle, and the throttle plate (2) does not pivot when I move the governor loop with the throttle lever. Note, when I pivot the plate manually with my fingers waggling the governor, the engine performs as it should, speeding up and down accordingly. See video link below.
I removed the shroud and cleaned out the debris that collected.

@senorcitizen. I'm pretty sure the throttle plate inside the carburetor operates as it should seeing as the speed of the engine does vary when I waggle the governor. See video.

@StarTech
Governor adjust bolt tightened as per instructions, and the area is now clean of debris.

Videos that better highlights my problem, one showing the unit with the shroud off, and another starting it up after your advice here. Any other tips grateful. My thanks

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