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SCORED
PISTONS
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A lean
run or fuel with inadequate lubrication can cause a hot spot
on the piston. This high temperature and lack of lubrication
will cause the alloy of the piston to gall In turn locking
the piston ring in the groove and rendering it ineffective.
Debris ingested through the engine will cause similar damage.
A bent
connecting rod can also cause seizure. See BENT
ROD
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The piston
alloy is also transferred to the cylinder wall.
A steel
cylinder can usually be repaired. An ABC cylinder usually
can not be repaired and must be replaced. ABC piston and cylinders
are matched sets and fitting a new piston to a used cylinder
in not available from any engine manufacturer. See
ABC
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A lean
run can be caused by several things, this incident was caused
by a split pressure line that supplied a fuel pump. Always
use new tubing and check existing tubing frequently. Pennies
invested can save Dollars in damage.
Other
culprits are...
Debris
in Carburetors
Incorrect Needle Settings
Wrong oil content in fuel
Pin holes in fuel lines
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A steel
cylinder can usually be saved with 280 or 320 grit Emery cloth.
Steel cylinders must have the glaze broken (roughened up) so
the new ring will seat properly. |
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Sand the
inside of the cylinder around the diameter, not up and down.
You can also use a brake hone for this.
You do
not want to remove metal, just roughen the surface.
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You should
have a nice "cross hatch" pattern with no sign of
alloy from the piston or any grooves.
If the
steel liner has a hard chrome surface like the K&B ringed
.61 the cross hatch pattern won't appear due to the hardness
of the chrome. Break in will take longer with this type of
liner.
If grooves
are apparent the ring will not seal the groove and optimum
compression will not be achieved. This will also cause blow
by. If this is the case replace the cylinder.
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