I have put 362 miles on my newly-built 505", so I pulled the plugs for an autopsy and replacement. These are NGK BKR5E, been in since initial fire-up and the subsequent driving.
Moving the timing and tune around some, working through the carb it's an older speed demon 850 mechanical-secondary and I've added replaceable air bleeds and PVCR's since they were all fixed on this model. I had it on my last engine too (440) and had it pretty well nailed, this time I'm thinking I might wanna add...
First plug change.
