I'll second that Stan's sealant. My son was remounting his tubeless MTB tires (needs to be done annually) and one had a puncture in it that you could see light through. I told him that he needed a new tire, and he just laughed at me, put in 2 oz of sealant and pumped it up a little. It oozed for a few seconds, and then stopped. A minute later, he pumped it up and that was it. He's been riding it all spring. Smarty pants kids.