As I worked through the various alignment issues I think I finally got it ready to go. The problem was the shaft on the new engine is not only longer but it isn’t milled down to 1″ all the way to the mower housing. The pulleys need to line up or the belts will lose power and could be damaged.
According to a friend that is a small gas engine repairman the shafts are cut off all the time if they are too long. The only problem is if your application gets something screwed into the end. If you cut it off you might not have enough threads left or the hole could be too shallow. In my case I’m using pulleys with a key-way and a set screw, so cutting the shaft was no problem.
However I did have a problem with the air supply to the cut-off tool I was using. My air compressor just couldn’t supply volume to run the tool, so I had to pause cutting and wait for the tank to fill back up with air. A better solution (other than a much bigger air compressor) is a cut off disk for my 4-1/2″ angle grinder. These cut of disks are very thin, which is a good thing as that means the cut is narrower so less material is removed which means less heat is generated. With any kind of metal-cutting heat is always a concern, if you were to just use a grinding disk it would cut a much wider slot and generate a lot more heat. It will also take more power from the tool so if you are at the limits of what it can do you might find your tool stalling out and maybe burning up the motor. If the piece you are working gets too how it can ruin the heat treatment.
Next step testing it out.