Curious as to what the function is of the floating valve on the front of the carburetor slide. Just got my daughter an '07 150RB and its giving me fits. Compression is right at spec. I have 1 exhaust valve .002 under (waiting for shims to correct) others at spec. Have cleaned the carb twice. Have a 138 main, 42 pilot, 60 bleed (50 on order) - came with a 150main and 48 pilot. Replaced aftermarket fuel screw with OEM one. Accelerator pump working correctly. Hot start valve is closing correctly. Replaced intake boot. Thing is a PIA to grt lit and refuses to Idle down. Spark "looks" good. Moving to ignition system next, but want to see if I overlooked anything in the carb. We run race gas in our bikes to avoid the moisture issues with pump gas. I've had 450r's since '06 so pretty familiar with the new thumpers - this is my first little guy though.