Troy-Bilt 78 Benutzerhandbuch

MTD builds horizontal crank engines for snow blowers and chore performers. The differences between snow 

engines and chore engines are the muffler and the air intake system. Therefore the air intake system for the snow 
and chore engines will be discussed separately, as will the mufflers in a later chapter.

One of the big differences between snow engines and all other small engines is that the air intake of the snow 

engine does not have an air filter. This is because air filters tend to freeze, cutting off air flow to the engine. The snow 
engine however does have a heat box to preheat the intake air.

The bottom of the heat box is open to draw in a large volume of cold air. The top of the heat box has a small 

opening were the choke rod connects to the carburetor. This draws in just enough warm air from the top of the engine 
to heat the cold air to the desired temperature as it enters the carburetor. 

To remove/replace the heat box:

1.     Pull off the choke and throttle knobs.

2.

Remove the control panel by taking off the five 
screws secures it using a 10 mm wrench.               
See Figure 3.1.

3.

Disconnect the wire from the ignition switch and the 
primer line from the primer button.

4.

Slide the breather hose out of the heat box.           
See Figure 3.2.

5.

Remove the two carburetor nuts using a 10 mm 
wrench. See Figure 3.2.

NOTE: When installing, tighten the carburetor nuts to a 

torque of 80 - 106 in-lbs. (9-12 Nm)

6.

Remove the choke selector assembly.

7.

Slide the heat box off of the carburetor studs.

8.

Install the heat box by following the previous steps in 
reverse order.

NOTE: There is no gasket between the heat box and the 

carburetor.

Remove these 

screws

Remove the
breather hose

Remove these 

nuts

For Parts Call 606-678-9623 or 606-561-4983

www.mymowerparts.com