B&S 10/12HP throttle repair

jaylees150

Forum Newbie
Joined
Jan 20, 2025
Threads
2
Messages
7
UPDATE

Having re visited this today in the daylight while I had some time, I have the throttle cable connected up and functioning properly. And I have the governor linkage and spring connected up as well. With the engine shut off I can manually push the throttle plate closed and it springs back nicely.

I re connected the battery and tried to start it with the throttle lever in the low revs position without success. As of right now I have nothing to connect the choke mechanism.
 

Attachments

  • 20250311_165404186_iOS (1).jpg
    20250311_165404186_iOS (1).jpg
    974.9 KB · Views: 6
  • 20250311_165352093_iOS (1).jpg
    20250311_165352093_iOS (1).jpg
    962.3 KB · Views: 6

bentrim

Member
Joined
Sep 7, 2024
Threads
0
Messages
23
See if this helps. In your pictures the spring appears at an angle, it should be limp and in a straight line when in the idle position and pull on the governor arm as the throttle is opened. It also appears the bracket is not properly attached to the block, the top bolt is missing, this may be why the governor is not functioning properly.
When the engine starts you are saying the engine goes wide open? This could be that spring incorrectly hooked up or the governor is out of adjustment or not functioning. Unhook the spring and start the engine, it should immediately go to idle. Push on the governor arm and it should have a force trying to close the throttle. if not you have a governor issue -- out of adjustment or a failed governor.
A governor works by balancing the force of the flyweights against the spring -- the more the spring pulls the more the flyweights attempt to pull the throttle closed. That balance is the speed that you set the throttle at. The more you open the throttle the more pull is applied to the governor arm. The flyweight then attempt to close the throttle but can't due to the applied spring pull.
The second attachment is NOT a verticle governor and does not apply to your engine but it is the best diagram I could find to explain how a governor works.
 

Attachments

  • carb linkage.PNG
    carb linkage.PNG
    169.7 KB · Views: 4
  • gov.PNG
    gov.PNG
    202.3 KB · Views: 2
Last edited:

slomo

Lawn Pro
Joined
Jul 14, 2019
Threads
78
Messages
5,280
UPDATE

Having re visited this today in the daylight while I had some time, I have the throttle cable connected up and functioning properly. And I have the governor linkage and spring connected up as well. With the engine shut off I can manually push the throttle plate closed and it springs back nicely.

I re connected the battery and tried to start it with the throttle lever in the low revs position without success. As of right now I have nothing to connect the choke mechanism.
Got to have some choke for cold starts.
 

jaylees150

Forum Newbie
Joined
Jan 20, 2025
Threads
2
Messages
7
See if this helps. In your pictures the spring appears at an angle, it should be limp and in a straight line when in the idle position and pull on the governor arm as the throttle is opened. It also appears the bracket is not properly attached to the block, the top bolt is missing, this may be why the governor is not functioning properly.
When the engine starts you are saying the engine goes wide open? This could be that spring incorrectly hooked up or the governor is out of adjustment or not functioning. Unhook the spring and start the engine, it should immediately go to idle. Push on the governor arm and it should have a force trying to close the throttle. if not you have a governor issue -- out of adjustment or a failed governor.
A governor works by balancing the force of the flyweights against the spring -- the more the spring pulls the more the flyweights attempt to pull the throttle closed. That balance is the speed that you set the throttle at. The more you open the throttle the more pull is applied to the governor arm. The flyweight then attempt to close the throttle but can't due to the applied spring pull.
The second attachment is NOT a verticle governor and does not apply to your engine but it is the best diagram I could find to explain how a governor works.
It's starting to look a lot better I think! I know that since I bought it it's never had the top bolt for that throttle plate, It doesnt appear to line up with the governor arm connected. I'm wondering if the governor arm should be to the left of the plate?
I can't seem to find many examples of this particular set up online to copy from.
 

Attachments

  • 20250314_165932478_iOS (1).jpg
    20250314_165932478_iOS (1).jpg
    938.2 KB · Views: 4

jaylees150

Forum Newbie
Joined
Jan 20, 2025
Threads
2
Messages
7
The missing number after the first digit is either a 5 or 8. If it is a 10hp, it will be a 5, and 12hp an 8. You need to get the full 4-digit spec number, as "015" doesn't match anything. It should be four digits like this: 0167. Use a wire brush to get it as clean as possible, and you should be able to read it from one angle or another and either a flashlight or not. Need that number. You have the incorrect carburetor on there; it looks like an Amazon 20-dollar special. Do you have the original? You are missing the linkage rods going from the throttle control to the carb as well as the choke linkage. Do NOT allow that engine to run wide open; it will destroy the engine quickly. Also, can you provide the full model number and serial of the tractor? Since the LT125 was made from roughly 1990-2010, if you provide the full model, it will be easier to narrow down the correct engine. Your governor spring is hooked incorrectly, as is your throttle rod linkage; it belongs in the top hole of the governor shaft.
This is the sticker that came from the rear of the mower. And after a significant amount of scrubbing and cleaning, I have determined that the engine model number is 252707 0151-01 780417.
 

Attachments

  • 20240503_212712.jpg
    20240503_212712.jpg
    947 KB · Views: 1
Last edited:

slomo

Lawn Pro
Joined
Jul 14, 2019
Threads
78
Messages
5,280
UPDATE

Having re visited this today in the daylight while I had some time, I have the throttle cable connected up and functioning properly. And I have the governor linkage and spring connected up as well. With the engine shut off I can manually push the throttle plate closed and it springs back nicely.

I re connected the battery and tried to start it with the throttle lever in the low revs position without success. As of right now I have nothing to connect the choke mechanism.
Is your fuel filter on backwards? Look for an arrow on the body.
 

kbowley

Well-Known Member
Joined
Jun 8, 2011
Threads
3
Messages
188
Is your fuel filter on backwards? Look for an arrow on the body.
Makes no difference; they have no check valve, and gas can flow either way.
 

Auto Doc's

Well-Known Member
Joined
Sep 7, 2024
Threads
1
Messages
157
This is an older engine, I would guess around the early 80's or older.
The model a type numbers are stamped in the top cover (flywheel shroud). Usually on the very back above the head, or on one side.

Let's resolve one post, call it fixed then move on to the second one. Get rid of the confusion.
At first glance, it has a wrong carburetor that someone put on it.
 
Top