Wessa

Hi all need to chat with someone who knows the Yamaha dt125r 98 inside out. Have a few problems. 1) bike has a flat spot around 4000 revs to 5000 revs then pulls fine. Any ideas how to solve or where to start looking. 2) when stopping I pull the clutch to drop into first or neutral and has problem going in. 3) oil coming out of the power valve. Changed the seal still sprats oil. many thanks hope seone can help.