Weird 14mm will usually be 110mm for BMX or 135mm for dirt jump bikes or similar, these are marketed as FGFS and are flip flop so could well be a strange 14mm 120mm thing, I've not seen bikes for these but guess they might make FGFS ones like it as they are like big BMX type things. I've filed a 14mm axle without a problem, it makes it a little more awkward to get the wheel in and out and you need to be careful to file the slots in the same place on either side. I probably wouldn't bother as it seems like a load of extra faf.
Weird 14mm will usually be 110mm for BMX or 135mm for dirt jump bikes or similar, these are marketed as FGFS and are flip flop so could well be a strange 14mm 120mm thing, I've not seen bikes for these but guess they might make FGFS ones like it as they are like big BMX type things. I've filed a 14mm axle without a problem, it makes it a little more awkward to get the wheel in and out and you need to be careful to file the slots in the same place on either side. I probably wouldn't bother as it seems like a load of extra faf.