Here's a picture of a rim that was filled with "stop a flat" or a similar corrosive. As you can see the rim is corroded which can cause a new tire to not seat properly and lose air.
Although stop-a-flat or other types of sealant product may seem like a good idea to seal a puncture on your scooter these products actually corrode the rim and eat through the paint on the inside of the rim.
When we receive a bike where the customer used stop-a-flat we will have to clean the rim completely and either sand off the corrosion or in extreme cases replace the rim. If you have to use these products make sure to get your bike into the shop ASAP before you damage the rim beyond repair. Any pitting or corrosion that cannot be sanded off will cause a slow leak between the tire and the rim because the tire bead will not seat properly.
Have fun and safe riding!
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