Hi Qwerty8, welcome to Outdoorking.
Our main SB45 guru, Deejay, is away from home due to a serious family health issue and may not be able to reply for a while, so I'll give you an interim report on what you have said about your mower.
Usually the reel has to be replaced for one of three reasons: it has been reground so many times that there is no "meat" left on the blades before reaching the disks they mount on; or it has been damaged by some kind of mishap and the individual blades are badly bent; or the axle is damaged and the whole reel is running out of true. Your reel does not show signs of any of these things, as far as can be seen from the photograph. However you need to rotate it, and see if the blades move closer to, then further away from, the bedknife as it rotates. If they do, the axle is bent and you have a fairly serious problem.
We would need some more detailed pictures to assess what is going on with the machine. The cork clutch lining looks all right in your picture, though it may have run out of adjustment and consequently slipped. If that happened, most of the time it is due to the clutch half that mounts on the engine's crankshaft having slipped along the shaft toward the engine, so that spring pressure is lost. It is easily corrected by adjustment, subject to the captive cotter pin not having deteriorated. If it has deteriorated, you will need a new engine-side clutch-half. The primary chain is not fitted in your picture, and the first sprocket is not visible, but the second sprocket looks to be in terminal condition and may have been slipping. The third sprocket looks downright weird - I'd need close-up pictures to try to assess what is going on there. Essentially though, you need new chains and sprockets, as do most well-used, but not well-maintained, old SB45s.
There seems to be red primer on the front frame rail, pretty much in the locations where that rail is prone to cracking if the machine has been run for a long time with an excessive vibration condition. It may be that there has been an attempt at repairing rail cracks, or cracks are still present. This is fairly difficult to fix, but by no means impossible.
In summary, from what I can see so far, your SB45 is in a bit worse than average condition for an SB45, but is well within the range of machines that our members regularly repair and put back to work. Assuming the reel is not damaged and just needs sharpening, the most serious problems seem to be the fairly awful state of the chains and sprockets, and the possibility that the front rail is cracked. Both problems are rather routinely found in old SB45s.
