Greetings...

Greetings!

My son's crf150f was running rough yesterday [backfiring-wouldn't rev smoothly] with choke in normal "off" position. Setting choke to half choke middle position allowed much smoother running. Spark plug had white color indicating too lean. I assumed carb needed cleaning. I removed carb - dismantled and spray cleaned everything with carb cleaner and reassembled. I was careful to put everything back in original position - including mix screw [1 3/4 turns out]. The air cut-off valve was tricky to reassemble but seemed right. But now bike will only start with choke set to midde or full choke. In middle position, will idle, but dies when throttle applied. It is ridable with full choke - so it sounds like it is starving for gas... yes? I plan to disassemble and check everything today, but any advice or shared experience with similar problem would be greatly appreciated. FYI... have been cleaning honda carbs for years - this is first time had a problem. What did I do wrong? Thanks in advance for your help!

DT

 

maybe your needle valve or float could be sticking a little bit? if not, i have no clue. carbs is not my expert area. I once rebuilt a 250 Suzuki, then went to start it, and tried for 3 days before i realized that the float was stuck. if it has a diaphram, maybe the diaphram in the carb has a pinhole in it, causing it not to provide suction properly. this would cause it to run lean too, (i think). try turning the air screw in some. if its running lean, then turning it in will cause it to get less air to mix with the fuel, making it equalize somewhat, a temporary fix.