I searched long and hard for an answer to this exact issue. Everyone eludes to the issue but no one seems to give any specifics. In my case, this EXACT issue was due to clogged "bypass holes" in the low speed circuit. This is Mikuni's terminology. Two VERY small holes in the throat of the carbs on the up stream side of the butterfly valve (when closed). Standard carb cleaning cleared the low speed hole but not these. Had to reinsert the low speed screw fully and then blow cleaner thought the low speed circuit to clear them. 100% corrected after that. As others mentioned, this is a lean condition. That's why choking improves the response but its still not right.
@@Xenuear Yes, RU-vid wont let me use links so you'll have to google it. Search Mikuni Super BN Owner's Manual. The link from EC Carburetors is the PDF. It is on page 7 labeled "BYPASS HOLES"
I crossed with this video and cause me trouble. The guy didn’t see oil not coming down into the carb. One way valve caused this problem or something on oil distribution lines. Also, running the poor jet ski like that is like sending to the grave.
