Billís Technoid

Technical Index

Proper Seating of Engine Oil Seal - Air Cooled

- Bill C. -

This addresses proper seating of the oil seal that is installed in the flywheel end of the case.

Of course, you have the engine removed; the clutch and pressure plate removed; and finally, the large gland nut and pressure plate removed.

  • It should fit far enough into the case that its outer surface does NOT protrude beyond the surrounding surface of the case. Gently tapping in with a light shot mallet or using an installation "washer" should be sufficient.
  • Failure to meet this requirement will cause early seal failure and/or interference with crankshaft endplay as the flywheel back (face) surface can rub against it.

What can prevent the seal from going in all the way?

  • Before installing the seal, check the bore into which it is going, for burrs, dings, etc., and gasket sealer/glue.
  • Carefully remove any burrs, etc., which protrude.
  • Be Careful! Donít remove case material other than protrusions! The case is magnesium.
  • Glue residue - Some engine builders use a gluey substance in the hope of obtaining a better seal against leaks. If this old glue is not removed, it can create enough "grab" that the seal will not easily install properly. I would suggest something no stronger than a metal brush.
  • Be Careful! Donít remove case material!