Since I've typed this all before
, I thank http://www.hydraglide.com
for a searchable knowledge base!:
Lapping works, sometimes.
There are occasions where even burnishing is not perfect.
The disadvantages of lapping are:
The unit must be completely disassembled for cleaning.
Metal is removed from the pump body, thus widening the seat.
A ball on a stick is not accurately piloted to the bore of the well.
The finish left by common compounds is comparable to the molecular size of oil.
Burnishing actually moves
metal. Low spots get filled as highs are reduced, on a micro level of course. In this process, the surface is work-hardend for longer life.
The pump must be removed from the motor for access on a 45", but only the breather line above the ballcheck must be removed for an OHV.
Three or four slow, creeping torques up to firm and solid does it. (~15 ft/lbs). Remove the burnisher, toss in a fresh ball and spring, cap it, re-assemble and rub off your fingerprints.
Damaged pumps require some extra attention, naturally. It is preferable to do any cutting on the bench where you can have total hygiene, but I have a piloted conical stone that I apply by hand to dress blemishes or rust prior to finish-burnishing. The flat side of the stone effectively narrows the seat.
We all know oil penetrates. That's why we use it in motors. An absolute seal is probably an un-attainable ideal.
What we hope to accomplish is to reduce seepage to where the machine can sit out of service for extended periods without filling the cases and overflowing at the sprocket shaft. (Some of us are embarrassed by such incontinence, especially when you leave a trail across the carpet and out the driveway.)
The time it takes to manifest itself not only depends upon the ballcheck, but the time between rides. And those with a sprocketshaft seal mask the problem until the cases completely fill and it blows out the breather.
By burnishing, it is possible to have a machine sit all winter (in a heated garage) and still have a full four quarts in the oiltank. I still personally find that amazing.
(Just in case a little more explanation of "burnishing" is needed:
When you tape up a package, and then run your thumb over the tape to flatten it, that's a very simple form of burnishing. Pressure from a moving tool smooths the surface. Rub the tape with a hard blunt object like the side of a pen, and the tape becomes inseparable from the cardboard.
With malleable metals, the surface layer is quite plastic and can be compacted as well as smoothed. This not only hardens the surface, it can be used to stiffen an object, or to straighten a hole. One of the most common form of metal burnishers are rounded precision plugs that are then pressed or beaten through a slightly undersized hole. More elaborate ones are often used as one would a broach, however they have blunt knobs instead of cutting edges, in increasing diameter along its length.
Some of the advantages of burnishing are speed, accuracy, finish, and lack of abrasives or chips.)
A ballcheck seat burnisher applies a concentrated moving pressure exactly where it is needed. Instead of removing metal, it rearranges it into a more durable form, with a microscopic profile comparable to Clover Compound 6-A, if not smoother
The tool is very very simple: