I went riding last week at Carnegie. Because it just rained, the place is very muddy. I went on a very think mud field for about 20 min and bike got stuck. I put in first gear and rev hard. It moved a short distance and stuck again. I end up have to drag it out of the muddy field. After I washed it up clean, the bike starts fine but doesn't run anymore. Feel like no lutch engagement at all. I can push the bike while its in first gear! Please let me know what is the problem and how to fix it. Thanks.