Columbia 978, Operator'S Manual

13

6

WARNING

Figure 13

Figure 15

Figure 14

Blade Care

Periodically inspect the blade adapter for cracks, 

especially if you strike a foreign object. Replace when 

necessary. Follow the steps below for blade service:

1.  Remove the bolt and the blade bell support which 

hold the blade and the blade adapter to the engine 

crankshaft. See Figure 13.

2.  Remove blade and adapter from the crankshaft.
3.  The blade may be resharpened by removing it and 

either grinding or filing the cutting edge keeping as 

close to the original bevel as possible. Do not attempt 

to sharpen the blade while it is still on the mower.

4.  It is 

extremely important that each cutting edge 

receives an equal amount of grinding to prevent an 

unbalanced blade.

NOTE: Improper blade balance will result in excessive 

vibration causing eventual damage to the engine and 

mower. Be sure to carefully balance blade after sharpen-

ing. Possible damage resulting from blade unbalance 

condition is not the responsibility of the manufacturer.
NOTE: Always remove blade from the adapter for testing 

balance. 
5.  The blade can be tested for balance by balancing it 

on a round shaft screwdriver. Remove metal from the 

heavy side until it balances evenly.

6  Before reassembling the blade and the blade adapter 

to the unit, lubricate the engine crankshaft and the 

inner surface of the blade adapter with light oil. 

7.  Install the blade adapter on the crankshaft with the 

“star” away from the engine. See Figure 13. Place 

the blade with the side marked “bottom” (or with part 

number) facing away from the adapter. Align the blade 

bell support over the blade with the tabs in the holes 

of the blade and insert the hex bolt.

8.  Tighten the hex bolt to the torque listed below:
Blade Mounting Torque
Center Bolt 450 in. lb. min., 600 in.lb. max.

To insure safe operation of your unit, ALL nuts and bolts 

must be checked periodically for correct tightness. 

Belt Care

1.  Disconnect the spark plug wire and ground it against 

the engine. 

2.  Drain the fuel tank or place a piece of plastic beneath 

the cap to prevent gasoline leakage. 

3. Place shift lever in the first position and tip the mower 

on its side. (air cleaner side of engine up).

4. Remove the blade and blade adapter as described 

previously.

5. Move rear height adjuster to the highest position. 
6. Using a 3/8” socket remove three hex screws holding 

the baffle to the deck. See Figure 13. 

7. Pivot baffle towards the rear of the mower. See Figure 14.
8. Remove the hex bolt holding the transmission to the 

mower housing. See Figure 14.

Maintenance

We do not recommend 
the use of pressure 
washers or garden 
hose to clean your 
unit. These may cause 
damage to electrical 
components, spindles, 
pulleys, bearings, or 
the engine. The use 
of water will result in 
shortened life and 
reduce serviceability.

When removing the 
cutting blade or belt, 
protect your hands 
with a pair of heavy 
gloves or use a heavy 
rag to hold the blade.

An unbalanced blade 
will cause excessive 
vibration when rotat-
ing at high speeds. It 
may cause damage 
to mower, and could 
break causing per-
sonal injury.

A

B

A

B

9. Tilt the transmission forward and loosen the idler 

pulley bolt and locknut ½ turn using two 7/16” 
wrenches. See Figure 15.