When you change the float level, that affects jetting. If it was leaking, try installing a new float needle, and set it to the correct specs. Go back to stock jetting and start from scratch.
Also, check to make sure there's enough compression. Without enough compression, it'll run really rich, foul plugs, ect.
Don't know if it has a powervalve. Look at the exhaust port area, is there anything that indicates a powervalve in the area?