# Troy-Bilt Bronco over-revving



## Declan (Jan 18, 2015)

Have a troy bilt Bronco mower with a B&S engine that started revving up high while mowing. Pulling the throttle all the way down did nothing. The RPM's kept increasing so I shut it off as to not blow the motor. Cable and throttle lever seem to be working fine. Governor spring is intact. 

This was my dad's last mower he bought before he died so I don't want to trash it and it costs $100 just to have the shop pick the thing up and bring it back, so I would rather not sink a fortune in pick up charges if it is something that can be addressed easily or cheaply.

Any suggestions as to where I need to begin with the repair?


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## Bearfootfarm (Jul 13, 2006)

You could try spraying it with carb cleaner while moving all the linkage.
It sounds like something inside the carb is stuck.

Add some Seafoam to the gas first


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## ticndig (Sep 7, 2014)

take the cover off that holds the pull rope . under the cover is full of leaves and such that is interfering with the governor .


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## Declan (Jan 18, 2015)

ticndig said:


> take the cover off that holds the pull rope . under the cover is full of leaves and such that is interfering with the governor .


It is a riding lawn mower with an electric ignition.


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## Declan (Jan 18, 2015)

Bearfootfarm said:


> You could try spraying it with carb cleaner while moving all the linkage.
> It sounds like something inside the carb is stuck.
> 
> Add some Seafoam to the gas first


I'll give it a try. I fear that the internal governor is sticking and if so, it would probably be cheaper to buy a new mower than have someone take the motor apart.


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## alleyyooper (Apr 22, 2005)

Even with electric start the engine has shrouding around it. It draws air in thru the top that goes around the shrod to cool the engine so shrod is removable.
*Cheaper to buy a new one than fix that one? Have you priced a new one, I know labor is high but not that high.*

Engine looks similar to this one.











Now with that all said sounds as if you are a rookie at engine work.
Go to the library and get a book on small engine repair. The newer the better, study that book from cover to cover before you do any thing else. Once you have studied the book find the section on how to remove the cooling shrod. tools required will probably be a Phillips and/or flat screw driver, a 7/16 box wrench or 10 MM. 
Being your first time take pictures as you remove bolts and screws for later replacement. 
Once the shroud is off clean all the debree away from those wire type linkages and lube them. *Do not use oil or grease to lube the linkage*. 
A lot of dust and dirt goes thru the area so you don't want a lube that will catch that stuff.
Use some thing like *dri slide *

Hope this helps.

 Al


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## Declan (Jan 18, 2015)

alleyyooper said:


> Even with electric start the engine has shrouding around it. It draws air in thru the top that goes around the shrod to cool the engine so shrod is removable.
> *Cheaper to buy a new one than fix that one? Have you priced a new one, I know labor is high but not that high.*
> 
> Engine looks similar to this one.
> ...


Sorry, I was wrong about the engine. My old one had a B&S engine. This one has a 20 HP Kohler engine in it. All the external linkage works fine and dandy. Yes I am a novice when it comes to opening up engines. Anything on the outside is fine. It is when I am having to pull an engine apart I am not so fine.

My brother called the repair shop mechanic and he said it sounded to him like the internal parts of the governor were sticking and that it would be "pricey but not sure how much depending on how long it took"


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## backwoodsman7 (Mar 22, 2007)

Declan said:


> Sorry, I was wrong about the engine. My old one had a B&S engine. This one has a 20 HP Kohler engine in it. All the external linkage works fine and dandy. Yes I am a novice when it comes to opening up engines. Anything on the outside is fine. It is when I am having to pull an engine apart I am not so fine.
> 
> My brother called the repair shop mechanic and he said it sounded to him like the internal parts of the governor were sticking and that it would be "pricey but not sure how much depending on how long it took"


Should be able to fix it yourself with the service manual, which you can download from Kohler's website. Ebay is a good source for inexpensive parts.

http://www.kohlerengines.com


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## jerrystead (Oct 19, 2011)

could be lean on fuel or a vacuum leak somewhere in the intake system, or a govenor issue.


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## Declan (Jan 18, 2015)

jerrystead said:


> could be lean on fuel or a vacuum leak somewhere in the intake system, or a govenor issue.


I think the internal governor. I bought a new mower but need to see if I can fix this one at some point when I have the time and cash


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## Murby (May 24, 2016)

I almost guarantee its something in the governor. 

To the above posters: there is nothing in a carb that could cause an engine to rev higher than the governor would allow. 

Have you kept up on changing the oil? If the oil gets too gummy, it could interfere with the internal governor paddles and cause them to stick. 

The governor paddles operate much like a centrifugal clutch assembly.. as the engine speeds up, the paddles spin.. the faster they spin, the larger their circumference becomes.. Sort of like spinning with a string and a weight in your hand.. the faster you spin, the higher and further out the weight gets pushed. There's a little mechanical assembly there that pulls on the governor linkage.. if ANY of that gets stuck, bound up, or seizes in any way, the engine could easily over-rev.

Start the engine and manually move the governor assembly to see if you can control the engine speed. You'll need to play with the throttle a bit so that you have enough rpms to activate the governor but not so much you over-rev the engine.

Might be a good idea to change the oil too... Don't they make an oil flush kit that de-gums engines? 

Spray a bunch of carb cleaner on all the governor linkage to clean it up and then re-lubricate with some light oil too.


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## Declan (Jan 18, 2015)

Murby said:


> I almost guarantee its something in the governor.
> 
> To the above posters: there is nothing in a carb that could cause an engine to rev higher than the governor would allow.
> 
> ...


Nothing happens when you move the throttle as far as the engine nor does playing with the external side of the governor. It just revs faster and faster.


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## Murby (May 24, 2016)

Declan said:


> Nothing happens when you move the throttle as far as the engine nor does playing with the external side of the governor. It just revs faster and faster.


Either I'm not reading you correctly or you're not making sense.

The engine can not run any faster than the amount of fuel it is getting. In other words, it doesn't matter if the engine is rigged to blow it self up, if you limit the fuel, you limit the rpms. (otherwise you'd be getting into an area of free energy!)

So, if you close the throttle, the engine should idle.. Try that first.. 
Take the air cleaner off so you an look down the carb body.. the butterfly plate closest to the air cleaner is the choke plate.. The plate below that is the throttle plate. 
Use the control lever and make sure the throttle plate is opening and closing properly. It may not close all the way depending on your idle stop screw setting but it should come close. 

Verify the throttle plate opens and closes and all the mechanical linkage from the carb body to the throttle lever on your machine. Basically, just have someone move the lever back and forth while you're looking down the carb (engine off!)

The throttle plate works by limiting the amount of air going into the carb.. By limiting the amount of air, you limit the amount of suction the carb generates.. by limiting the amount of suction, you limit how much fuel is pumped into the engine.

Does the throttle plate work? 
While you're there messing with it, see if the carb is securely screwed to the engine head.. make sure its not flopping around or anything.


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## Declan (Jan 18, 2015)

Murby said:


> Either I'm not reading you correctly or you're not making sense.
> 
> The engine can not run any faster than the amount of fuel it is getting. In other words, it doesn't matter if the engine is rigged to blow it self up, if you limit the fuel, you limit the rpms. (otherwise you'd be getting into an area of free energy!)
> 
> ...


The throttle works. From the throttle to the carb, everything moves the way it is supposed to. It just doesn't change anything. Nothing stops it from reving though. It just runs full blast.


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## Murby (May 24, 2016)

Declan said:


> The throttle works. From the throttle to the carb, everything moves the way it is supposed to. It just doesn't change anything. Nothing stops it from reving though. It just runs full blast.


Start it up and block the carb intake and see what it does. This has to be done with the air cleaner off so you get a good seal.

If the engine doesn't get air, it can't run. If it still runs when you block it off, then its sucking air in from somewhere its not supposed to.


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## jerrystead (Oct 19, 2011)

the govenor is usually a separate thing from the actual throttle, and there is usually a linkage between the governor and the throttle, make sure that you are truly moving the throttle (on the carburetor and not just the governor). A vacuum leak can definitely do what your saying though because when there is a vacuum leak in the intake system there is extra air entering just like as if the throttle were being opened except that its leaner on fuel. A vacuum leak can and will make an engine rpm up without a doubt, not saying thats your problem, but a very real possibility


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## jerrystead (Oct 19, 2011)

if you can move the govenor and the engine does not change rpm, then another possibility in my mind would have to be that the linkage has came loose from the carburetor, so like I said make sure that you are truly moving the throttle shaft on the carb or first make sure that the govenor linkage is securely attached so that when you move the govenor the throttle shaft on the carb moves solidly with it. A vacuum leak can definitely make it rev, but if the govenor is making zero difference on RPM then there is a disconnect somehow between the govenor and the carb.


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