Ducati valve seal mod for a Norton

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May 4, 2005
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Has anyone heard of the Ducati valve seal mod for the Norton? After replacing the orignal valve seals twice already, my local bike shop is suggesting doing this mod. Would like more info before proceeeding. Is this a one way mod? If it doesn't work can I go back to the original seals? Are the seals commonly available?
What's wrong with the standard seal? I you fit them correctly and don't crush them they work.

I have had the head rebuilt 2 times now in the last 3 years. Both times there was oil leaking in 1 cylinder or another. Both times it turned out to be the valve seal that let go. The first time was a major rebuilt as the PO had butchered the valve job. The second time was a miner rebuild basically valve guides and valve seals. The mod was suggested to see if that would resolve the problem, as I have oil leaking into the cylinder again.

Yesterday I replaced the valve seal myself for the third time, will see how long this one lasts.
Are you sure the valve guides are not loose? Driving or pressing out the guides without first cleaning the carbon from the port side can enlarge the holes in the head. It is also advisable to heat the head prior to removing the old guides and installing new ones. Oversize guides are available to repair this.

I have never had a problem with Norton valve guide seals.
Have you used Viton seals? there are some realy crap rubbery seals around. (Nitrile perhaps)

The Viton seals I use come from RGM and they are black. I'm sure that's all they sell now.

The valve guides were replaced both times, I am assuming they are not loose,did not check before putting the head back together, but will be doing it over the winter. Both time there seals were damaged, especially the lip. The current seal I replaced were black but I could not say what type as I did not know of the various types available, but will for the next time. As usual the information given by the members of this forum is outstanding, thanks to all.
Viton components are often coloured for identification but they're often plain black as well... I think the only way you'll find out what you've got is to ask the supplier.
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