To prevent coking in the first place, keep the lines cooler, e.g. by putting a radiation shield between the lines and whatever heat source is nearby.
To dissolve coke that's already present without disassembling anything, run a few gallons of Marvel Mystery Oil through the lines, e.g. by adding it to the fuel supply. Directions for dosing are on the bright red can, ~$10/gal at Pep Boys.
Mike Halloran
Pembroke Pines, FL, USA