Model Engine Company of America

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

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

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

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.

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.

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.


The above information is provided as a guide. Since MECOA/K&B has no way of determining the ability of the individual using and understanding this information, we assume absolutely NO RESPONSIBILITY for any damage to person or property from the use of this information.

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