Throttle Shaft Seal Bobcat 743

[MikePhua]

Background of the Bobcat 743
The Bobcat 743 compact track loader, built in the 1990s, has earned a reputation for its rugged simplicity and long-lasting performance—powered by a reliable Kubota V1702 diesel engine and favored by small contractors and farmers. Its modest 1,300 lb rated operating capacity and straightforward mechanics make it affordable and dependable even decades later. 
Issue with Throttle Shaft Seal
A recurring problem on this model involves oil leakage where the throttle shaft exits the engine’s mounting plate. The issue often stems from a worn seal or bushing that allows oil to escape. Below are insights from seasoned technicians:

• In many cases, a bushing supports the throttle shaft, fitted into the housing via light interference (press fit).
  
• A seal, commonly an O-ring, encircles the shaft to prevent oil escape.
  
• Over time, the O-ring can harden, wear, or the bushing can develop play—resulting in oil seepage and shaft movement. 
  

Accessing the Seal
Despite limited space, accessing and replacing the seal is feasible:

• The throttle cover is held by four nuts—removal of this cover provides access. 
  
• The throttle arm is typically secured with a roll pin and can be driven out to remove the arm.
  
• With the arm removed, the bushing can be gently pressed out from the housing, allowing the O-ring to be retrieved and replaced. 
  

Repair Tips and Suggestions

• It’s practical to carry a standard O-ring kit, but for a precise fit, obtain the specific O-ring part from a Bobcat or Kubota dealer.
  
• When installing the new seal, applying a bit of clean oil on the O-ring helps ease installation and protects it from damage.
  
• If there’s excessive lateral play in the shaft after replacement, inspect or replace the bushing—excess movement indicates wear.
  

Real-World Anecdote
An operator from British Columbia noticed oil dripping around the throttle plate and mild side-to-side play in the throttle lever. After removing the cover and using photos from a colleague, he identified and acquired the correct O-ring. Replacing the seal eliminated the leak, and with the new part in place, shaft stability improved—even with heavy usage in sawmilling operations.
Preventive Maintenance & Additional Insights

• Include a quick check of shaft motion and seals during routine service—prevent small leaks from becoming larger problems.
  
• Keep the area clean, especially if operating in wood shavings or dusty shops, as debris can exacerbate leakage and wear.
  
• If a bushing shows extensive wear or oval deformation, consider replacing it with a new bushing—machined or ordered through parts channels.
  

Summary of Steps

1. Remove the throttle arm (via roll pin) and plate cover (four nuts).
   
2. Extract the worn bushing (press fit) and O-ring.
   
3. Clean the area thoroughly.
   
4. Apply oil to the new O-ring and install it into the bushing housing.
   
5. Reinstall the throttle arm and test for smooth action and no leakage.
   
6. Observe for lateral play—replace bushing if necessary.
   

Conclusion
Even though the Bobcat 743 is a decades-old design, its throttle shaft seal repair remains straightforward. With a press-fit bushing and O-ring sealing, a few well-placed tools and a correct replacement part can restore proper function and eliminate oil seepage. Regular visual checks and timely replacement keep this compact loader running clean, safe, and dependable well into its second generation of service.