After searching through 120 threads about the athena kit I'm still scatching my head. I have a 2001 yz125, everything is stock except the works 125 kit from athena that comes with the cylinder, power valves, flat top piston and high comp head. everything is installed and the bike runs. the topend power rips my arms off. By far one of the fastest 125s I've ever been on. The issue I'm having is the bottom end power is not there. Now I know you're saying "it's a 125 there is no bottom". It is borderline 4stroke boggin on me which leads me to believe it's a jetting issue. I'm running 110 race gas from the race track down the road at 32:1. The kit instructions suggested 104 oct but I could only find 110 near me. I'm in FL at sea level, and weather is in the 70-80s. It has the stock 460 main jet in it and like i said it rips high speed. It had a stock 25 pilot jet which I replaced with a 22.5 pilot with no success. I've moved the clip down and up with again no success. I've played with the air mixture screw with no help there either. the plug is golden brown and looks perfect. This bike is going to be mainly used in the woods for hare scramble racing so a little bottom end would be nice.