I had a similar problem with an ancient Suzuki GS 650 a few years back -- and it did shut down at speed.
The problem turned out to be the ignition coils.
Yours kind of sounds like a faulty new battery though.
Intermittent nature could indicate a bad cable. If the power comes back on when you jiggle the cable -- well there you go.
Barbarosa
Similar situation on an HD I had... the rectifier was bad, so riding for a while discharged the battery enough to cause it to either fail to restart or shut down while riding. Let is sit for about 5 minutes and you could light it off again.
> Barbarosa
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Cheers,
Chief mailto:ch...@saftek.com