After 6 months, I think I might have found a solution.
I spotted that the Sonaca 200 (a certified aircraft with a Rotax 914) has aluminium banjo unions connecting the fuel pressure regulator to fuel hoses with AN6 flare fittings. These banjo unions fit over M10 banjo bolts that screw directly into the engine's pressure regulator. As Jeffry notes above, these aluminium AN flare banjo unions are wider than the standard steel barb Rotax banjo unions (13mm vs 9.9mm). This means that the 19mm long banjo bolts supplied with the engine as standard are too short to connect the 13mm wide aluminium M10 to AN6 unions safely to the pressure regulator.
I was lucky enough to be offered an opportunity to inspect the Sonaca arrangement. I discovered that the M10 banjo bolts used in the Sonaca installation are 23mm long, not 19 mm long. The banjo bolts used in the Sonaca installation seem otherwise identical to the 19mm long bolts supplied by Rotax as standard for the fuel pressure regulator.
Further research led me to discover that Rotax supply 23mm long banjo bolt as part of the 914 oil system. The part number is 940876 (M10 x1 x23 banjo bolt).
Can anyone see any reason not to adopt the approach that Sonaca appear to use in a non-certified context? That is, attach AN6 banjo unions to the fuel pressure regulator using the 23mm long banjo bolts normally used in the oil system?
Thanks
