Well in order to prevent Andy having to repeat himself too much, here is a useful hint.
Seeing as there is no readily accessible way to search the main site??

you can type <searchwords> site:nsr-world.com into the search bar of the Google Chrome web browser to easily search the main site.

In this case "head gasket site:nsr-world.com" is possibly quite useful

And as some people seem to sometimes get poor results some of the time from using the forum search, (yes, a debatable point) may I suggest this:
<searchwords> site:nsr250.net/forums

For example "exup site:nsr250.net/forums"

Just trying to be helpful.
Not meaning to criticise NSR-World.
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[color=#808080][size=9]Yes,.. I too know how to waste Time and Money,...