I re-piped my brakes on the R100 yesterday. Single pipe from master cylinder down to right hand caliper and then a second pipe running from the right hand caliper to the left. Banjo bolts required. Pipe between calipers loops over front mudguard, just behind the fork leg.
What I found that works well, in the traditional way, is to fill the master cylinder and then lightly feather the brake lever - i.e. tickle it until air bubbles stop finding their way up through the master cylinder into the reservoir. Once the master cylinder is properly primed, it will efficiently push fluid down the pipes. Air will still work its way to the top, and should be dealt with the same way by tickling the lever.
Took us less than half an hour to bleed the system from dry. nice and firm now.
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