Oil pump or drive failure

HI guys, I am new to the site, which is nice by the way! I have just recently bought a used 1991 Polaris Indy 440 sport, the PO said when he bought it he rode it for 6mi then it blew up, he took it to a motorsport shop and they said the oil injection had failed and the engine needed rebuilt so they rebuilt it $750 and told him it would be another $300 to fix the oil injection, he told them not to fix it and that he would just premix the fuel,,,,, Now I own it and I am wondering if it OK doing it this way??? I have heard like the exiter 440 would not get oil to the crank bea rings this way, am I ok with my Polaris pretty mixing for now anyways? ??? I may fix the oil injection later

Oil pump or drive failure