The old reliable NGK's are hard to beat.
Just be sure to replace them with the correct type and hear range.
The ones used on RC51's are the iridium type.
They come pre-gapped from NGK because the tip is very small and could be easily damaged.
So don't bother gapping them.
The iridium tipped plugs aren't cheap, but last a long time.
From the service manual, for temperatures above 41 Deg F.
'00-'06: (MSRP about $12.30 ea.)
'00-'01: (MSRP about $7.50 ea.)
Last edited by SubSailor; 03-12-2009 at 04:11 PM.