I revived an SL650 that had been sitting for about 18 years. I rebuilt the carbs (needle & seat, gaskets, diaphragms, did NOT change jets but cleaned them), replaced all fuel lines and upgraded to a 3 output fuel pump. I didn't realize there was a difference in the needle springs included in the kit. It had this same bogging problem, but otherwise ran pretty good. Turns out I did not seat one of the gaskets correctly and had a fuel leak. I pulled the carbs off to fix the leak, and decided to put the original springs back in while I had it apart. Pop-off pressure is right about 15, if not slightly less.

What happens is when I hit the throttle from idle, it bogs. I have to let off the throttle and then ease into it (couple seconds) in order to be able to run WOT. I found that if I hold the choke at about 1/2 way at idle and then hit the throttle, it will work ok. Still not great, but I don't have to let up in order for it to take off.

I'm guessing this is a lean condition, based off what happens when I use the choke, but I don't know if it's lean low or lean high.

Any suggestions?