The last few times I mowed the lawn, the tractor has stalled out. I try to restart it but all it does it turn over. I will let it sit for hours and then it will restart and I can use it for a while and then it will stall out again. It is gravity fed so no fuel pump and it seems to be getting spark. Any thoughts on why it keeps doing this? It didn’t do it at all during the winter while using the snow blower. Thanks