Warning, Caution, Maintenance and repair instructions – MTD 1642AVCC User Manual

Page 14

SAW CHAIN TENSION ADJUSTMENT

Proper tension of saw chain is extremely important and
must be checked before starting, as well as during any
cutting operation.

Taking the time to make needed adjustments to the saw
chain will result in improved cutting performance and
prolonged chain life.

To adjust the saw chain:
1. Loosen bar nut, hold nose of guide bar up and turn

adjustment screw (D) CLOCKWISE to increase chain
tension. Turning screw COUNTERCLOCKWISE will
decrease amount of tension on chain. Ensure the chain
fits snugly all the way around the guide bar (Fig. 22).

Always use
protective gloves

when handling the saw chain.

WARNING:

Fig. 23

Fig. 22

2. After making adjustment, and while still holding nose

of bar in the uppermost position, tighten the bar
retaining nut securely. Chain has proper tension
when it has a snug fit all around and can be pulled
around by gloved hand.

NOTE: If chain is difficult to rotate on guide bar or if it

binds, too much tension has been applied. This
requires minor adjustment as follows:

A. Loosen the bar retaining nut so it is finger tight.

Decrease tension by turning the bar adjustment
screw COUNTERCLOCKWISE slowly. Move chain
back and forth on bar. Continue to adjust until chain
rotates freely, but fits snugly. Increase tension by
turning bar adjustment screw CLOCKWISE.

B. When saw chain has proper tension, hold nose of bar

in uppermost position and tighten the bar retaining
nut securely.

A new saw chain
stretches, requiring

adjustment after as few as 5 cuts. This is normal
with a new chain, and the interval between
future adjustments will lengthen quickly.

CAUTION:

saw chain is TOO

LOOSE or TOO

TIGHT, the sprocket, bar, chain, and
crankshaft bearings will wear more rapidly.
Study Fig. 23 for information concerning
correct cold tension (A), correct warm
tension (B), and as a guide for when saw
chain needs adjusdjtment (C).

CAUTION:

Fig. 24

CHAIN BRAKE MECHANICAL TEST

Your chain saw is equipped with a

Chain Brake

that

reduces possibility of injury due to kickback. The brake
is activated if pressure is applied against brake lever
when, as in the event of kickback, operator’s hand
strikes the lever. When the brake is actuated, chain
movement stops abruptly.
To Test the

Chain Brake

1. The

Chain Brake

is DISENGAGED (chain can move)

when BRAKE LEVER IS PULLED BACK AND
LOCKED (A, Fig. 24).

2. The

Chain Brake

is ENGAGED (chain is stopped)

when brake lever is in forward position. You should
not be able to move chain (B, Fig. 24).

NOTE: The brake lever should snap into both positions.

If strong resistance is felt, or lever does not move
into either position, do not use your saw. Take it
immediately to a Authorized Service Center for
repair. Call 1-800-520-5520 for more information.

The purpose of the

Chain Brake

is to

reduce the possibility of injury due to

kickback; however, it cannot provide the

intended measure of protection if the saw is

operated carelessly.
Always test the Chain Brake

before using

your saw and periodically while on the job.

WARNING:

REMOVING AND INSTALLING THE GUIDE BAR

1. Make sure the

Chain Brake

lever is pulled back into

the DISENGAGED position (Fig. 17).

2. Remove the bar retaining nut (B1) and the screw (B2)

at rear of clutch cover (C). Remove clutch cover (C)
by pulling straight out, some force may be required.
(Fig. 18). Remove bar and chain.

3. To install bar, place the slotted end of the guide bar

over the bar bolt (F). Slide guide bar behind clutch
drum (G) until the guide bar stops (Fig. 19).

INSTALLING A CHAIN

1. Spread chain out in a loop with cutting edges (A)

pointing CLOCKWISE around loop (Fig. 20).

2. Slip the chain around the sprocket (B) behind the

clutch (C). Make sure the links fit between the
sprocket teeth (Fig. 21).

3. Guide the drive links into the groove (D) and around

the end of the bar (Fig. 21).

NOTE: The saw chain may droop slightly on the lower

part of bar. This is normal.

4. Pull guide bar forward until chain is snug. Ensure all

drive links are in the bar groove.

5. Install the clutch cover. Make sure the chain does

not slip off of the bar. Install the bar retaining nut
hand tight and follow tension adjustment instructions
in the next section. Replace screw at rear of clutch
cover.

NOTE: The guide bar retaining nut is installed only hand

tight at this point because saw chain adjustment
is required. Follow instructions in Saw Chain
Tension Adjustment.

Always use
protective gloves

when handling the saw chain.

WARNING:

To ensure the bar and
chain receive oil, ONLY

USE THE ORIGINAL STYLE BAR with the oil
passage hole (A) as illustrated in Fig. 17.

CAUTION:

Fig. 17

Fig. 18

Fig. 19

Fig. 20

Fig. 21

MAINTENANCE AND REPAIR INSTRUCTIONS

This manual is related to the following products:

1425NAV 1842AVCC