I ran into the same problem,so I dropped one tooth in the back to a 40 tooth.Worked like a charm.

 

Extending the curved slot is very easy fix. The axle and both wheels come right off with only two bolts. Extending the slots takes another hour or so. Running without roller or with incorrectly adjusted chain or with worn chain/sprockets on a Banshee is a VERY risky situation. The chain can come off, pack up into the front sprocket, and break the engine cases. This can lead to a very expensive case replacement or in many situations just leads to the early retirement of a good 4 wheeler when the quad isn't worth the cost of repair.

 

Alright ill look into it. I dont have time to do it before the ride this weekend but when i get back ill yank her apart and see what i can do. What would be a good tool for cutting those slots bigger?