Silly question (sorry, it's been stretched out over threads and time, so I forget!) but have you swapped CDI packs top to bottom to see if the problem switches barrels?

How about switching coils? Same problem? Top cylinder still?

New plugs, new battery? Have you tested the charging circuit - especially with the bike running?

It very much sounds like something electrical breaking down if you say it initially ran OK. A pink spark really would indicate something in the system breaking down.
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Andy.
NSR-WORLD.COM

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