Hi seanw,
Well I hope that you are sitting really comfortably or better still are laying down totally relaxed, as sadly I'm in the unenviable position of having to be the bearer of bad news for your lovely little Scotty.
After having a look at you photos, which I was really impressed with, I found a major discrepancy which is not an easy fix, rather it's an easy one in the sense of just R&R, but it's going to be painful (ouch) on the hip pocket.
To cut to the chase you must replace your reel, why you ask, well sadly some unscrupulous mower repair shop has given the machine to the apprentice to reassemble after doing that unorthodox bottom blade reversal and they probably cross threaded the nut on the end of the reel shaft. So to get themselves out of trouble they ground off butchered thread and tack welded the shaft directly to the cutter sprocket.
How flamin' stupid and irresponsible can one be !!!!!
This was probably done because they knew the owner would never ever remove the chain case (that's why they had the mower in the first instance) and discover their medical malpractice. To make matters worse the welds have cracked and the only thing that's holding it all together is the woodruf key and the raised height of the welds on the shaft restricting lateral movement of the sprocket.
The only thing that will fix this is by carefully grinding back the welds on the shaft so that the sprocket can be removed and the weld dags on the face can be filed back to a flat and serviceable condition. Alternatively if you are good with a cutting wheel on a grinder you could simply cut the shaft off and finely grind it back to the sprocket face and then the sprocket should slide off.
Now your major issue here is to obtain a replacement 14 inch reel, which can be obtained second hand out of a defunct electric 45 as they are monetarily worthless and can be picked up for around $60 or less at best which is far less than the cost of a new reel, that's for sure and no one is going to give you a reel out of a petrol powered machine.
Apart from that the rest of the machine is quite salvageable and would restore up very nicely, especially with it being one of the very last SB Model 45 14 inch examples.
Now if you don't want to proceed with the repairs I can totally understand, but remember there's a guy in South Australia that would really like to tackle your little beauty and bring it back to it's former glory, but if you are prepared to go the distance I'm here to help you through the bad times so to speak.
Cheers,
BB
