I own a 2007 polaris sportsman 450. I upgraded me tires to a more aggressive tread but same size tire. Was out riding one weekend and noticed when I got into the mud or water so high it would dog out and I would actually be in the mud in high and it would rev high but tires wouldn't barley turn. Shortly after that I noticed I had a carb boot to my air box that was tore off the carb. I replaced that and my air filter but still has major lack of power in the mud will barley turn the tires. Now on the flat it runs strong but the moment I actually go on a incline it falls flat on its face. Need serious help trying to figure out what could be wrong. Thanks

 

Probably glazed/burnt the belt. Easy to check when you take the cover off. Just pull the belt up and off,look close for any shiny burnt spots. Plus if you can push down on the middle of the belt with a straight edge over top of both clutches and the distance between top of belt and straight edge is 1 1/2" or more,I'd replace the belt anyway. Usually they'll run ok when it's not under a load,but on inclines or under a load the belt starts slipping,engine revs.Also if you can not a bad idea to check for any wear on the rear clutch drive buttons before they possibly wear too far and damage the clutch and helix. Not to scare you,just preventative maintenance as I've seen many that went too far and clutches were trashed. Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse