JB’s Front seal cutter for XPAG engines

(from Michael Sherrell #689, Perth, Australia).

(Mike sent this to the Octagon ‘Bulletin’ in response to a query raised by one of their members…. Ed)

It is easy to forget just how long ago our remarkable XPAG engines were designed. Retaining the oil in the engine was not the priority it is in today’s ‘perfect’ world.

Here I quote from my Green book ‘TCs Forever-More!’ page 75:

“(Again,) there are variations on the original ‘dog’s turd’ involving half-hearted attempts to fit a lip seal in its place. Now we have to turn to our own John Bowles once again for inspiration. J.B. devised a simple hand cutter, piloted off the crankshaft pulley threads to cut into the face of the timing cover and the sump at the same time, and so producing a round hole of appropriate size for a ‘Viton’ lip seal to run on the crank pulley boss. Ordinary ‘black’ lip seals will not do, as 5/6000 revs is a bit much for them. Naturally, the sump and gasket need to be fully bolted up for this operation. Replacement is simply a matter of removing the crank pulley. This time the original engineering solution was sadly lacking. Enough said. It was a long time ago.”

cutter shown piloted off the crankshaft

The small spindle passes through the centre of cutter head and threads into end of crankshaft with starter dog and pulley removed. A small handle at the rear drives the cutter forward by hand, a little at a time, while the two large handles turn the cutter.

This cutter is set in stages (not one big cut) to make a concentric hole in the face of timing cover and sump as one. The operator must make sure the hole being cut is as small as possible, ideally to fit a Viton seal of 36. 47. 7. dimensions, cutting only the front face into the void, (and not right through!). If the hole does not clean up at 47, then a slightly larger o/d seal may be needed.

In worse case, a steel ring may be required to house the standard seal.

(Not to scale)