Harley Ironhead Valve Lapping

Life's a bitch...   Thank God there's Harleys...

T made these pictures of L lapping the valves of our Ironhead engine. We realize that valve lapping is not the highest standard in professional engine rebuilding practice, but given the fact that the valve seats of our Ironhead engine heads did not show too much wear - and no damage - we figured that under our circumstances lapping the valves and valve seats should be perfectly acceptable.

Lapping the Valves of our Sportster Ironhead Engine

Valve lapping means you are spinning the valve in its seat, whereby you apply a lightly abrasive paste or polishing compound between the valve and the seat. In this way you polish both surfaces for a perfect fit.

Valve lapping is usually done using a round stick with a rubber suction cup at one end. You fix the suction cup to the flat face of the valve, apply the lapping paste to the valve, and then spin the valve in its seat by twisting the stick between your fingers or the palm of your hand.

L&T chose for the easy way. They clamped the valve stem into an electric screwdriver, pulled it gently against the valve seat, then polished the valve onto the valve seat by spinning the valve back and forth at low speed. The polishing paste does the work.

Valve Lapping

Valve lapping is just for polishing. If a valve or valve seat has scratches or other damage, valve polishing by lapping is not the solution. In that case, valve grinding will be required.

L&T used two grades of polishing compound: fine and extra fine.

April 2009