125ml to 5 litres is 25-1 which is good for a 2 stroke on running the piston in.
i use to run my yz at 20-1,20ml to each litre and it was fine.
to rich will kill your plug plus best to turn the fuel off when finished riding and run the fuel down so it cuts its self out.
50-1 is 50ml to each litre 250ml to 5 litres.
if i am wrong sorry but this is how i ran my 2 motox and never had any problem.
cheers darren