Rust not manufacturer issue. But paint in the belt groove can cause all kinds of havoc on belts and should be considered a manufacturing issue, not a defect in quality but in workmanship. But I say the OP either has a belt alignment issue or could be something like welding spatter in a pulley...
Agree Rivets. Could be something as simple as a rough area on a pulley that is filing the belt down. Had a rider years ago that had issues with damaging the belt because of paint that had partially chipped off of the pulley in the groove and was acting like a knife to the belt.
May also want to pop the fuel line loose from the carb and check fuel flow through the fuel line. Should be full flow and if trinkling out means fuel restriction. I have seen the fuel filter that gets inserted into the fuel outlet on the fuel tank collapse and cause flow issues. Also some of...
Next time it stalls try loosening the gas cap and see if it will restart. Also could try putting a small amount of gas into the carb intake and see if it starts and dies or continues to run. Or doesn't start at all.
May want to recheck the model number because it is coming back to a 1993...
Looks like the float pin is still in place at the bottom of your picture. That has to come out to remove the float. If the float doesn't come out then the float valve is stuck and will need to be pried out. then you can get to the emulsion tube screws after that.
Most of the courage twins used the non solenoid shift starters. If you are looking to do the conversion to the solenoid shift starter version see this thread
https://lawnmowerforum.com/threads/sv740-starter.76195/
Which has the part number for the solenoid shift starter that I used on the...
Lets start with the actual model and serial number from the tag on the mower since P510 really doesn't mean much. Also numbers from the engine may also help.