How to Replace the Drum and Sprocket on a Poulan Pro Chainsaw

The drum and sprocket drive your chainsaw's chain. The drum is installed over the clutch and has the sprocket attached to it. A needle bearing is pressed into the drum. When the saw is throttled-up, the clutch expands, contacting the drum and causing it to spin. The drum will wear after years of use. It can be burned or warped if the saw is accidentally run with the brake engaged. The sprocket will wear from constant contact with the chain. After years of use, the needle bearing can also wear out.

Let's get started.

REMOVING THE DRUM AND SPROCKET   1. Remove the side cover.

a. Loosen the two nuts securing the side cover to the saw.
b. Use a screwdriver to loosen the tensioning screw and release the tension from the bar.
c. Remove the nuts securing the side cover to the saw.
d. Verify that the chain brake is disengaged (unlocked).
e. Remove the side cover.
  2. Remove the chain.

a. Slide the bar back (toward the rear of the saw).
b. Disengage the chain from the front sprocket on the bar.
c. Disengage the chain from the rear sprocket.
d. Remove the chain from the saw.
  3. Remove the bar.

a. Slide the bar off the mounting studs and remove it from the saw.
  4. Remove the clutch.

a. Use a clutch removal tool (and an impact driver) to loosen (and remove) the clutch.
  5. Remove the drum and sprocket.

a. Slide the drum and sprocket assembly off the shaft. (There are washers on both sides of the assembly.)
b. Retain the washers for reinstallation.

INSTALLING THE NEW DRUM AND SPROCKET

  6. Install the drum and sprocket.

a. Install the outer (smaller) washer onto the shaft.
b. Install the new drum and sprocket onto the shaft.
c. Install the inner washer (larger) over the new drum and sprocket.
d. Reinstall and tighten the clutch.

REASSEMBLING THE UNIT

  7. Reinstall the bar.

a. Install the bar onto the mounting studs.
b. Slide the bar back (toward the rear of the saw) as far as it will go.
  8. Reinstall the chain.

a. Install the chain onto the rear sprocket.
b. Align the chain driver links with the groove along the top of the bar.
c. Install the chain onto the front sprocket (on the bar).
d. Slide the bar forward to bring the chain into alignment.
  9. Reinstall the side cover.

a. Install the side cover.
b. Thread the bar nuts onto the mounting studs to hold the side cover in place (leave the nuts finger-tight).
  10. Tension the chain.

a. Grasp and raise the distant end of the bar and chain assembly (near the sprocket).
b. Rotate the tensioning screw to increase tension on the chain.
c. Periodically lift the chain away from the bar assembly and inspect the gap between the chain and the top of the bar. (You should be able to lift the chain slightly out of the groove in the bar, but not so far that an entire driver link is exposed.)
d. Rotate the tensioning screw to increase (or decrease) tension on the chain (as necessary).
e. Tighten the nuts to secure the bar and chain.