I bought a 1959 d4 7u with in seat starting. I see all kinds of videos of people starting there machines from the side sitting on there tracks. But I can't find any videos or information on the in seat starting. Some videos or information on this would be helpful for when I go pick up the machine. Thank you

check out the library tab for the various D4 7U manuals. knowing your serial number will help much. sorry i can't be of more help. welcome

Serial number is 7U43982.

i can give you the basics but not ever ever seen the seat start option you will need to adapt. there should be some way to turn the gas on for the pony/a lever or knob that engages or disengages the compression release for the big engine/another knob or lever that operates the pinion/ and another for the pinion clutch. the throttle for the big engine should open close the fuel for the big engine.

Instructions for in seat starting can be found in the "Operation and Maintenance Instructions" book for the #955 Traxcavator ( which is where in seat starting for the D4 originated).
Most functions are obvious if your familiar with pony start.
The knob/lever on the left is the starter pinion and clutch control.  All the way in is brake applied, out is clutch engaged position.
Lever on the dash RH side by the choke and throttle knobs is the compression release. Left is decompression, right is run position.