On a standard NSR MC21 head the plug is quite shrouded. I was surprised at how ugly shrouded the standard NSR250 MC21 heads are.
Following Wobblys suggestion I spot faced the plug seat back 2.5mm. Maybe a good idea for any standard NSR250 head too.
The idea of a one off lots of work bespoke center plug rainbow head is pretty useless when you are building several engines and looking for repeatable practicality.
When I have figured out how to produce easily repeatable no compromise center plug heads I will be able to make a back to back dyno comparison with my original modified NSR head, and maybe with a completely standard one too, it will be interesting to see how that goes.
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