The engine in the Genie GTH-644
Fitment for the Genie GTH-644 centres on the Perkins 1104C-44T 1104D-44T: 4.4L / 268 cu in, 4-cyl inline, 105 x 127 mm bore x stroke, about @ 2200 rpm, Tier 3. Serial number on the block settles the exact version. New-surplus and rebuilt stock ships from Houston.