Oregon Harvester Handbook page 90

Guide Bar Troubleshooting
9. Rail chipping in the middle of guide bar.
Cause: Excessive pressure on the guide bar, excessive guide bar
feed speed, cold conditions, lack of lubrication, aggressive saw chain
when cutting in frozen wood .
Symptoms: Damage to the saw chain and reduced guide bar life .
Remedy: Replace the guide bar if rail wear is extensive . Decrease the
guide bar feed force when cutting consists mostly of small-diameter
trees . Increase lubrication, especially in cold conditions . Reduce
aggressiveness of the saw chain when cutting frozen wood .
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Mechanical Timber Harvesting Handbook
7. Blue spots at the tail of the
guide bar.
Cause: Misaligned drive sprocket
or rails pinched because debris not
removed from saw pad or guide bar
when the guide bar was installed .
Symptoms: Blue spots on rails
indicate temperatures reaching 600° F
(315° C) and softened rails . Rails wear
quickly . Saw chain drive link damage .
Remedy: Realign drive sprocket and
guide bar using proper shims . Clean
the guide bar and saw pad when
installing a guide bar . Replace the
saw chain .
8. Spread rails.
Cause: (1) Saw chain was struck
broadside by tree, log, or branch stub .
(2) Saw chain was pushed sideways,
forcing drive links to pry guide bar
rails apart .
Symptoms: Guide bar will not enter
log during cut or cannot make a
complete cut .
Remedy: Hammer rails together with
a drive link in the groove as spacer .
Adjust the saw return to allow the
guide bar to go farther into the saw
box . Sharpen delimbing knives . Avoid
moving the tree/log when the guide
bar and saw chain are out of the saw
box . Reduce the guide bar feed speed .