he was a convicted felon, no knives allowed
Plus he was on probation. Freddy knew he had an illegal knife. That is why he ran from the bike cops cuz if they caught him with it he was going back to the slammer.
He was also most likely on probation for one or more of his numerous crimes, in which case there would be various restrictions on him... such as possessing weapons and hanging out with other criminals.
The cops knew this guy well, and I'm sure they knew what he was up to... and so did he, which is why he tried to run away the second the cops saw him.