Rings the things

Practical Sportsbikes (UK) - - Fettling -

I’ve had my Du­cati 900SS from new so it has very few un­known hor­rors. Oil is weep­ing from both cylin­ders at the rear of each head/ cylin­der joint (no head gas­kets on th­ese). Less than 10,000 miles ago the en­gine was prop­erly stripped and re­built by spe­cial­ists to ad­dress the com­mon oil gal­ley plug is­sue. Also, new pis­tons and rings were fit­ted and the heads were re-torqued af­ter run­ning in.

All ap­peared fine un­til a few hun­dred miles ago. Now fol­low­ing a thor­ough clean of both bar­rels I’m now at least 99 per cent cer­tain oil is weep­ing from the high­pres­sure oil feed route at the head to bar­rel mat­ing faces. But how might a brand new O-ring fail if prop­erly seated in place and not dis­turbed in any way? Wayne Har­vey, emai

Jonathan Sewell says: If it’s not a Vi­ton seal, but a generic rub­ber O-ring, it will fail af­ter a while through ex­po­sure to heat. And it’s al­ways a good idea to lap the heads to the bar­rels too, much like lap­ping in a valve. This gives the sur­faces a much bet­ter chance to seal.

Vi­tal to use Vi­ton seals not generic O-rings

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