I asked a question yesterday about initial carb settings for a 1997 Yamaha Timberwolf. Now I found out that it has an aftermarket exhaust pipe. The factory pilot jet is a #20, and the main jet is a #85. Any ideas on what the next step would be. The atv basically runs out of fuel at the top of each gear/rpm.

 

Sounds like your main is too small, running out of fuel.