How To: Triumph garter oil seal

A milling machine makes converting a pre-unit Triumph crank feed to a garter oil seal a DIY job.


1: I use an old valve body attached to a steel strip to clamp the timing cover to the mill bed. Position the cover so the bore for the original bush is dead central to the spindle and lock the table.

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2: Then bore the hole with a 1in cutter. The hole is off-centre in some castings, but there’s still room... just. These spacers represent the depth I need to bore the hole...

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3: ... the thin one is the thickness of the seal, the thick one is the seal and circlip. To cut the clip groove, use an adjustable boring head. Offsetting the casing slightly counters the eccentric hole...

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4: ... to avoid the groove breaking through. But even if it does it will still secure the seal. More easily replaced, an oil seal also gives better oil pressure than the original bronze bush.

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